Bacterial infection induces nitric oxide synthase in human neutrophils.

The identification of human inflammatory cells that express inducible nitric oxide synthase and the clarification of the role of inducible nitric oxide synthase in human infectious or inflammatory processes have been elusive. In neutrophil-enriched fractions from urine, we demonstrate a 43-fold increase in nitric oxide synthase activity in patients with urinary tract infections compared with that in neutrophil-enriched fractions from noninfected controls. Partially purified inducible nitric oxide synthase is primarily membrane associated, calcium independent, and inhibited by arginine analogues with a rank order consistent with that of purified human inducible nitric oxide synthase. Molecular, biochemical, and immunocytochemical evidence unequivocally identifies inducible nitric oxide synthase as the major nitric oxide synthase isoform found in neutrophils isolated from urine during urinary tract infections. Elevated inducible nitric oxide synthase activity and elevated nitric oxide synthase protein measured in patients with urinary tract infections and treated with antibiotics does not decrease until 6-10 d of antibiotic treatment. The extended elevation of neutrophil inducible nitric oxide synthase during urinary tract infections may have both antimicrobial and proinflammatory functions.

A multiple ligand-binding radioimmunoassay of diiodotyrosine.

A radioimmunoassay has been developed for the measurement of 3,5-diiodo-L-tyrosine (DIT) in serum. DIT was coupled to porcine thyroglobulin (PTg) with a molar ratio of 205:1. Rabbits were immunized with 1 mg of immunogen emulsified in complete Freund's adjuvant. Sera were screened for their ability to bind trace amounts of [125I]DIT. A serum that bound 40% of the tracer at a final dilution of 1:1,750 was used in the assay. Assay specificity was improved by the use of thyroxine (T4)-binding globulin as a second ligand-binding protein to decrease T4 and triiodothyronine (T3) cross-reactivity with the antibody. Double antibody and polyethylene glycol radioimmunoassays were compared. DIT present in the second antiserum shifted the double antibody assay standard curve and altered estimates of assay specificity and assay sensitivity. By using the polyethylene glycol system and butanol:ethanol extracts of serum, DIT was measured in human serum. In 35 apparently healthy young adult controls DIT levels averaged 156 ng/100 ml. Random DIT levels averaged 158 ng/100 ml in 11 untreated hyperthyroid patients and 84 ng/100 ml in 15 untreated primary hypothyroid patients. No diurnal pattern in DIT levels could be demonstrated. Thyroid-stimulating hormone administration led to a variable but small rise in DIT levels, but short term T3 suppression was not associated with a measurable fall in DIT concentrations. Paired serum samples from the carotid artery and thyroid vein of 10 euthyroid goiter patients and one patient with a toxic solitary adenoma all showed a positive transthyroidal gradient indicating the thyroidal release of DIT in each patient. Measurable DIT levels of 45, 47, 68, and 80 ng/100 ml, respectively, were found in four fasting athyrotic patients indicating that the thyroid is not the only source of serum DIT.

Cardiac hypertrophy is not a required compensatory response to short-term pressure overload.

BACKGROUND: Cardiac hypertrophy is considered a necessary compensatory response to sustained elevations of left ventricular (LV) wall stress. METHODS AND RESULTS: To test this, we inhibited calcineurin with cyclosporine (CsA) in the setting of surgically induced pressure overload in mice and examined in vivo parameters of ventricular volume and function using echocardiography. Normalized heart mass increased 45% by 5 weeks after thoracic aortic banding (TAB; heart weight/body weight, 8.3+/-0.9 mg/g [mean+/-SEM] versus 5. 7+/-0.1 mg/g unbanded, P<0.05). Similar increases were documented in the cell-surface area of isolated LV myocytes. In mice subjected to TAB+CsA treatment, we observed complete inhibition of hypertrophy (heart weight/body weight, 5.2+/-0.3 mg/g at 5 weeks) and myocyte surface area (endocardial and epicardial fractions). The mice tolerated abolition of hypertrophy with no signs of cardiovascular compromise, and 5-week mortality was not different from that of banded mice injected with vehicle (TAB+Veh). Despite abolition of hypertrophy by CsA (LV mass by echo, 83+/-5 mg versus 83+/-2 mg unbanded), chamber size (end-diastolic volume, 33+/-6 microL versus 37+/-1 microL unbanded), and systolic ejection performance (ejection fraction, 97+/-2% versus 97+/-1% unbanded) were normal. LV mass differed significantly in TAB+Veh animals (103+/-5 mg, P<0.05), but chamber volume (end-diastolic volume, 44+/-6 microL), ejection fraction (92+/-2%), and transstenotic pressure gradients (70+/-14 mm Hg in TAB+Veh versus 77+/-11 mm Hg in TAB+CsA) were not different. CONCLUSIONS: In this experimental setting, calcineurin blockade with CsA prevented LV hypertrophy due to pressure overload. TAB mice treated with CsA maintain normal LV size and systolic function.

Reversibility of diabetes- and diuresis-induced alterations in rat bladder dome muscarinic receptors.

Previous studies from our laboratory demonstrated that 8 weeks of streptozocin (STZ)-induced diabetes and sucrose-fed diuresis resulted in increases in the density of muscarinic receptors in rat bladder dome and that early insulin treatment (started 3 days after the onset of diabetes) prevented the diabetes-induced upregulation (J Pharmacol Exp Ther 248:81-88, 1989; Diabetes 40: 1150-1156, 1991; J Urol 147:760-763, 1992). To determine whether diabetes- and diuresis-induced alterations in muscarinic receptors in rat bladder dome are reversible, we administered insulin (beginning 8 weeks after the onset of diabetes) or removed sucrose from drinking water of diuretic rats (beginning 8 weeks after the onset of diuresis). Five groups of rats were maintained for 16 weeks: 1) STZ-induced diabetic rats (65 mg/kg intravenously); 2) insulin-treated diabetic rats (5-8 U/day insulin subcutaneously beginning 8 weeks after the onset of diabetes); 3) sucrose-fed diuretic rats (5% sucrose in drinking water throughout 16 weeks); 4) sucrose-removed rats (sucrose withdrawn from drinking water after 8 weeks of the sucrose-induced diuretic state); and 5) age-matched control rats. Radioligand receptor binding experiments with [3H]quinuclidinyl benzilate showed an increase in the density of muscarinic receptors in bladder dome of diabetic and sucrose-fed rats compared with age-matched control rats. Removing the 5% sucrose from the drinking water of diuretic rats reversed the increased water intake and urine output, decreased the bladder hypertrophy that accompanied the diuretic state, and corrected the upregulation of the muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential regulation of bladder beta-adrenergic and muscarinic cholinergic receptors in experimental diabetes.

To determine the contribution of diuresis-induced bladder hypertrophy, which accompanies the diabetic state, on the biochemical and functional alterations observed in the diabetic bladder, we compared three experimental groups: 8-wk streptozocin (STZ)-induced diabetic rats, 8-wk sucrose-fed diuretic rats, and age-matched controls. Diabetic and sucrose-fed rats had higher water intake, higher urine output, and larger bladders than controls. Diabetic rats had lower serum insulin levels, lower body weights, and higher serum glucose levels than either control or sucrose-fed animals. Receptor binding studies with [3H]quinuclidinyl benzilate in bladder dome demonstrated an upregulation of muscarinic receptors in diabetic and sucrose-fed rats compared with controls. Parallel binding studies with [3H]dihydroalprenolol and [125I]iodopindolol showed an upregulation of beta-adrenergic receptors in diabetic but not in sucrose-fed bladder domes. Carbachol induced larger contractile responses in diabetic and sucrose-fed than in control bladder dome muscle strips. isoproterenol relaxed KCl-contracted detrusor strips from both diabetic and sucrose-fed rats to a greater degree and with a higher affinity than detrusor strips from controls. Our data show that overdistension and increased workload per se contributed to the upregulation of muscarinic but not to the upregulation of beta-adrenergic receptors in STZ-induced diabetes. Furthermore, the magnitude of carbachol-induced contractions correlated with muscarinic receptor upregulation, whereas the magnitude of isoproterenol-induced relaxation did not correlate with changes in the density of the beta-adrenergic receptors. Thus, it appears that different regulatory mechanisms are involved in diabetes-induced alterations in muscarinic and beta-adrenergic receptors in bladder dome.

Accurate preoperative diagnosis of pericardial constriction using cine computed tomography.

OBJECTIVES: The purpose of this study was to determine the accuracy of cine computed tomography in the diagnosis of constrictive pericarditis. BACKGROUND: Constrictive pericarditis is characterized by abnormalities of both cardiac structure and function. Accurate diagnosis requires detection of both a thickened pericardium and abnormal ventricular diastolic filling. At present, no one diagnostic technique has demonstrated sufficient accuracy in this setting. Cine computed tomography is a relatively new cardiac imaging mode with very high time and spatial resolution that has the potential to accurately diagnose constrictive pericarditis. METHODS: Twelve consecutive patients were retrospectively identified who had catheterization findings suggestive of constrictive physiology, had undergone a cine computed tomographic examination and had pathologic data that delineated the status of the pericardium. Group 1 (with constrictive pericarditis; n = 5) had surgical confirmation of thickened pericardium and improved clinically after pericardiectomy. Group 2 (no constrictive pericarditis; n = 7) had cardiomyopathy with normal pericardium. Seven normal volunteers (Group 3) were also studied. Cine computed tomograms were obtained for the entire heart (8-mm slices, 17 frames/s, nonionic contrast medium). Pericardial thickness was measured at 10 degrees intervals at three ventricular levels in each subject. The rapidity of diastolic filling was assessed by calculating the percent filling fraction in early diastole. RESULTS: Pericardial thickness was 10 +/- 2 mm (mean +/- SD) in Group 1, 2 +/- 1 mm in Group 2 and 1 +/- 1 mm in Group 3 (p < 0.05, constrictive pericarditis vs. no constrictive pericarditis). Left ventricular filling fraction was 83 +/- 6% in Group 1, 62 +/- 9% in Group 2 and 44 +/- 5% in Group 3. Right ventricular filling fraction was 93 +/- 5% in Group 1, 62 +/- 14% in Group 2 and 35 +/- 6% in Group 3 (p < 0.05, Group 1 vs. Groups 2 and 3). Both indexes provided a clear-cut distinction between patients with and without constriction. CONCLUSIONS: Cine computed tomography simultaneously provides both anatomic and physiologic data that allow accurate preoperative diagnosis of pericardial constriction.

Quantitation of absolute regional myocardial perfusion using cine computed tomography.

OBJECTIVES: The purpose of this study was to develop and test a method for quantitation of regional myocardial perfusion using cine computed tomography. BACKGROUND: Cine computed tomography is a relatively new cardiac imaging technique with excellent temporal and spatial resolution. Application of this technique to the study of human coronary circulation could substantially broaden our knowledge of human cardiac pathophysiology. This goal has been previously approached with some success. However, no method to date has shown validated accuracy of regional perfusion measurements over the entire range of physiologically important flow states. METHODS: Eight anesthetized dogs underwent thoracotomy for instrumentation. They were then studied during baseline flow conditions, after coronary vasodilation with intravenous dipyridamole and after coronary stenosis or occlusion. Regional myocardial perfusion was assessed by cine computed tomography using a method that includes estimates for myocardial blood volume and rate of myocardial enhancement after an aortic root contrast medium infusion. Measurements made nearly simultaneously by the radioactive microsphere method served as a reference standard. RESULTS: A total of 32 perfusion conditions were studied with a range of 4 to 593 ml/min per 100 g. There was reasonable agreement between the two methods of measurement throughout the whole range of perfusion states: r = 0.97, regression slope 0.99, intercept 2 ml/min per 100 g. In zones not subserved by a stenosed or occluded artery, cine computed tomography accurately depicted perfusion homogeneity with a coefficient of variation of 13 +/- 1% (mean +/- SE) versus 11 +/- 1% for the microsphere method (p = NS). CONCLUSIONS: Cine computed tomography is capable of providing accurate, quantitative assessment of regional myocardial perfusion over a broad range of perfusion states. This method, if extended to the study of humans, could enhance the understanding of disorders of the coronary circulation in human cardiovascular disease states.

Patterns of regional diastolic function in the normal human left ventricle: an ultrafast computed tomographic study.

The detailed evaluation of regional diastolic filling at multiple ventricular levels in the normal human left ventricle has not previously been reported. Ultrafast computed tomography was used to characterize global and regional early diastolic filling in the left ventricle of 11 normal male volunteers. Regional early diastolic filling data from six distinct ventricular levels (apex to base) were fit to a third-order polynomial curve, and the peak rate of diastolic filling and time of peak filling were determined. Peak filling rate was 259 +/- 17 ml/s (+/- SEM) as a global average, where peak filling rate referenced to end-diastolic volume and stroke volume across the levels examined was 3.78 +/- 0.17 s-1 and 4.83 +/- 0.20 s-1, respectively. Average filling fraction was 39 +/- 1%, and time to peak filling from end-systole was 145 +/- 5 ms. Regional (tomographic) peak filling rates, except for the most apical level examined, were not statistically different across the ventricle. Filling fraction and time to peak filling were remarkably constant from one level to another. However, reference of regional peak filling rate to regional end-diastolic volume demonstrated significant nonuniformity from apex (120% of average for all levels) to base (87% of average for all levels). Peak filling rate referenced to tomographic stroke volume was less variable and not statistically different across the ventricle as a whole.(ABSTRACT TRUNCATED AT 250 WORDS)

Antioxidants attenuate myocyte apoptosis in the remote non-infarcted myocardium following large myocardial infarction.

OBJECTIVE: Increased oxidative stress and myocyte apoptosis co-exist in the remote non-infarcted myocardium (RM) following a large myocardial infarction. We proposed that these phenomena are causally related. METHODS AND RESULTS: On day 3 after induction of myocardial infarction, Sprague-Dawley rats were randomized to receive probucol and pyrrolidine dithiocarbamate (MI-T), or vehicle only (MI) for 7 weeks. Control rats (C) received vehicle. At 7 weeks, lipidperoxidation within the RM was assessed by measuring thiobarbituric acid reactive substances, which were significantly increased in MI vs. C, while MI-T was not different from C. There was a significant increase in cardiac myocytes positive for in situ TdT-UTP nick-end labeling within the RM in MI vs. C, which was inhibited in MI-T. Furthermore, internucleosomal DNA fragmentation was clearly demonstrated on agarose gels from RM in the MI group, while it was much less apparent on gels from RM in the C and MI-T groups. Western blot analysis showed a significant increase in p53, Bax and caspase-3 protein expression within the RM of MI vs. C, all of which were inhibited in the MI-T group. Furthermore, there was evidence for an increase in caspase-3 activity within the RM from MI vs. C, which was normalized in the MI-T group. CONCLUSIONS: Long-term treatment with the antioxidants probucol and pyrrolidine dithiocarbamate attenuates oxidative stress, myocyte apoptosis, caspase-3 like activity and the expression of p53, bax and caspase-3 within RM in rats after a large myocardial infarction.

The effect of serum dilution on free thyroxine (T4) concentration in the low T4 syndrome of nonthyroidal illness.

Progressive dilution of normal sera causes little change in free T4 concentrations. Similar dilution of sera containing drug inhibitors of T4 binding to serum proteins causes a progressive fall in free T4. The low T4 syndrome of nonthyroidal illness is thought to be associated with a circulating inhibitor(s) of T4 binding. It would be expected, therefore, that dilution of sera from the low T4 syndrome might also result in a fall in free T4 concentrations. We compared the effect of progressive serum dilution on free T4 concentrations in low T4 syndrome sera to those in normal, hyperthyroid, pregnancy, TBG-deficient and salicylate-containing sera. A tracer dialysis method proved inappropriate for studying dilution effects. Using a new dialysate RIA method to measure free T4, we found a progressive fall in free T4 concentrations in sera from patients with the low T4 syndrome similar to that in serum containing salicylate, but not to that in normal sera. The magnitude of the fall varied widely among individual patients. Free T4 methods which use a diluted serum sample will underestimate free T4 concentrations in the low T4 syndrome.

Underestimates of serum free thyroxine (T4) concentrations by free T4 immunoassays.

Different free T4 (FT4) assays often give different FT4 measurements, and conflicting measurements have been striking in nonthyroidal illness. Because FT4 immunoassays depend upon serum protein-bound T4 (PBT4) dissociation to stabilize the FT4 concentration during assay perturbations, interassay differences in perturbations combined with variation in serum PBT4 concentrations could produce discordant FT4 measurements. This study examined the effects of PBT4 on FT4 measurements obtained by direct immunoassay methods. Standard solutions with constant FT4 levels and varying PBT4 concentrations were prepared and analyzed by direct equilibrium dialysis, two-step immunoextraction, one-step labeled T4 antibody, and one-step labeled T4 analog FT4 methods. Direct equilibrium dialysis results were independent of PBT4 concentrations and gave correct measurements of serum FT4 when the PBT4 concentration was above 8 nmol/L or 0.6 micrograms/dL, but were PBT4 dependent and underestimated serum FT4 at lower PBT4 concentrations. The other three methods were PBT4 dependent and variably underestimated serum FT4 at all levels of PBT4 up to 256 nmol/L (19.9 micrograms/dL), the highest level studied. Thus, PBT4-dependent underestimates of serum FT4 occurred with all four methods, whereas the measured FT4 level at each PBT4 concentration varied widely between methods. A serum PBT4 dependent bias causes discordant FT4 measurements and probably explains the observed underestimates of FT4 in nonthyroidal illness.

Serum diiodotyrosine.

Serum diiodotyrosine (DIT) was measured by radioimmunoassay in healthy subjects patients with thyroid disease and a variety of laboratorty animals. Ninety-two healthy adults had a mean level of 101 ng/100 ml. There was no sex difference in DIT levels but DIT fell with aging. There was no change with short term oral SSKI administration. Athyrotic subjects had measurable but reduced levels (mean = 52 ng/100 ml). Hyperthyroid subjects had levels slightly, but not significantly, higher than controls (mean = 149 ng/100 ml). Treatment of hyperthyroidism was followed by a small but significant fall in DIT levels, but there was no change in DIT levels with thyroid hormone therapy of hypothyroidism. A large species variation in serum DIT levels was found among laboratory animals with mean levels ranging from 17 ng/100 ml in mice to 428 ng/100 ml in dogs.

Variable expression of 5 alpha-reductase deficiency: presentation with male phenotype in a child of Greek origin.

A male infant with perineal hypospadias and a small phallus bound in chordee is described. Biochemical investigation at age 9 months after hCG stimulation revealed a testosterone to dihydrotestosterone (DHT) ratio of 40, a markedly elevated value suggestive of deficient steroid 5 alpha-reductase activity. The diagnosis of 5 alpha-reductase deficiency was confirmed by elevated urinary 5 beta/5 alpha-steroid metabolite ratios and demonstration of defective 5 alpha-reductase activity in cultured fibroblasts from the patient's scrotum and foreskin. Application of DHT cream to the patient's abdomen raised circulating levels of DHT to the adult male range. Two courses of DHT given nightly for 3 and 4 months resulted in phallic enlargement. Surgical release of the chordee and hypospadias repair have resulted in normal male appearance of the genitalia. This case illustrates the heterogeneity of the 5 alpha-reductase deficiency phenotype.

Ultrafast computed tomography in the diagnosis of cardiac disease.

Ultrafast computer tomography (CT) is one of the major new imaging modalities that has become available for the evaluation of patients with heart disease. With cine CT it is possible to obtain high resolution images of the heart at 58-ms intervals. The inplane resolution is 0.7 to 1.5 mm, and the slice thickness is 3 to 9 mm. Images require the intravenous injection of nonionic contrast agents to obtain quantitative information about cardiac function. Cine CT has thus far been used in 3 general areas that relate to the evaluation of patients with heart disease: evaluation of cardiac structure and function, evaluation of vein bypass graft patency and flow reserve, and measurements of regional myocardial perfusion. Because of the outstanding spatial resolution of the images, it is possible to obtain very precise information about cardiac structure and function. The weight of the left ventricle and right ventricular walls can be measured to +/- 5%, and the stroke volumes and end-diastolic volumes of all 4 cardiac chambers can also be measured with an accuracy of +/- 5%. With this technology it is possible to determine the magnitude of aortic regurgitation within +/- 5 to 8%. This modality has also proved useful in the diagnosis of surgically resectable left ventricular aneurysm and a multitude of other cardiac disorders that involve abnormalities in cardiac structure, including congenital heart defects, aortic aneurysms and constrictive pericarditis. These diagnostic procedures use the peripheral injection of usually about 100 ml of contrast media and can ordinarily be completed in less than 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of residual ischemic myocardium within prior infarct zone for identifying patients at high risk late after acute myocardial infarction.

This study examines the prognostic implications of ischemia within the territory of a prior acute myocardial infarction (AMI) vs ischemia at a distance, which develops late after AMI. Sixty-one consecutive patients who underwent both exercise thallium-201 (TI-201) imaging and cardiac catheterization for evaluation of chest pain that developed after discharge from the hospital for AMI form the study group. Mean interval between infarction to the TI-201 study was 10 +/- 17 months. Initial and 2-hour delay TI-201 images were analyzed quantitatively to determine the presence and location (within vs outside the prior infarct zone) of TI-201 redistribution, a marker of ischemic viable myocardium. TI-201 imaging results were separated into 3 groups based on presence and location of TI-201 redistribution: no significant TI-201 redistribution was found in 16 patients; in 29, TI-201 redistribution was confined to the infarct zone; and in 16, TI-201 redistribution was outside the infarct zone. Stepwise multivariate logistic regression analysis was used to examine the comparative ability of TI-201 results and other patient variables to predict cardiac events. For total cardiac events (cardiac death, recurrent nonfatal AMI, unstable angina and coronary revascularization), both the presence of any TI-201 redistribution and multivessel angiographic coronary artery disease were significant predictors. However, when coronary revascularization was excluded as an endpoint, TI-201 redistribution limited to the prior infarct zone was the only significant predictor of cardiac events. All 8 cardiac events occurred in patients with T1-201 redistribution limited to the infart zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of myocardial ischemia as predictor of training effect in cardiac rehabilitation after acute myocardial infarction or coronary artery bypass grafting.

Exercise capacity increases to a variable degree in coronary patients during cardiac rehabilitation. The effect of baseline exercise-induced ischemia on the response to a 12-week conditioning program was evaluated in 106 coronary patients. The magnitude of exercise conditioning response was greater in nonischemic patients than in ischemic patients, with maximal exercise intensity increasing 69 versus 50% (7.2 to 12.1 vs 7.1 to 10.6 METs) (p less than 0.05) and maximal oxygen consumption increasing 28 versus 10% (23.1 to 29.6 vs 23.0 to 25.4 cc/kg/min) (p less than 0.05). Markers of conditioning during submaximal exercise such as heart rate and heart rate-systolic blood pressure product were similarly reduced in both groups. The groups did not differ by age, diagnosis, resting ejection fraction, incidence of beta-blocker use, maximal exercise capacity, maximal exercise heart rate, blood pressure or intensity of actual exercise training. These results suggest that exercise-induced ischemia alters the stimulus to adapt to exercise training.

Regulatory effect of experimental diabetes on the expression of endothelin receptor subtypes and their gene transcripts in the rat adrenal gland.

Endothelins (ETs) mediate paracrine control of vascular tone and secretion of steroids and catecholamines in the adrenal gland through two ET receptor subtypes, ETA and ETB. The differential distribution and function of these subtypes are responsible for the multiplicity of endothelin actions in this tissue. This study examines the regulatory effects of experimental diabetes on the gene expression, subtype specificity and localization of ET receptor subtypes, ET isopeptides, and endothelin-converting enzyme-1 (ECE-1) in the rat adrenal gland. The densities, pharmacological properties and distribution of ET receptor subtypes ETA and ETB in adrenal glands from streptozotocin-induced diabetic, insulin-treated diabetic and age-matched control rats were investigated, using radioligand receptor binding and autoradiographic techniques. The gene expression of ETA and ETB receptors ET-1, ET-3 and ECE-1 was evaluated using relative multiplex reverse transcription/PCR. The induction of diabetes caused a marked reduction in body weight but no significant change in adrenal gland size. The density of ET receptors was significantly increased in the diabetic rat adrenal gland, mainly because of an increase in the expression of ETB receptors. Insulin treatment normalized the diabetes-induced changes in the expression levels of ET receptor subtypes to control levels. The expression level of ET-1 mRNA was up-regulated, whereas ET-3 mRNA was down-regulated in the diabetic adrenal gland compared with the controls. The ECE-1 mRNA level in the adrenal gland was not altered by the induction of diabetes. Autoradiographic studies showed that ETA and ETB are the predominant receptor subtypes in the adrenal medulla and cortex respectively. These results suggest that ETA and ETB receptors are differentially distributed and regulated in the diabetic rat adrenal gland.

Muscarinic receptors in diabetic rat prostate.

To investigate the effects of experimentally-induced diabetes on prostatic muscarinic cholinergic receptors, the binding characteristics of [3H]quinuclidinyl benzilate ([3H]QNB) to prostatic membrane particulates were examined in four groups of rats: control, diabetic, diabetic insulin treated, and diabetic myo-inositol treated. Diabetes was induced by i.v. injection of streptozotocin (STZ), 65 mg/kg. Diabetic and diabetic myo-inositol-treated rats had hyperglycemia, hypoinsulinemia, glucosuria, polydipsia, and polyuria as well as significantly smaller prostates and lower body weights compared to control and diabetic insulin-treated animals. The densities of muscarinic receptors (Bmax) as determined by saturation studies with [3H]QNB in the prostatic plasma membranes of control, diabetic, diabetic insulin-treated and diabetic myo-inositol-treated rats were 80 +/- 8, 51 +/- 5, 78 +/- 3, and 47 +/- 7 fmol/mg of protein, respectively. [3H]QNB binding to muscarinic receptors was inhibited by muscarinic antagonists with the following rank order of Ki values: atropine much less than pirenzepine less than AF-DX 116. The pharmacological profile of the muscarinic receptors was similar in all groups examined and was consistent with the predominance of the M3 muscarinic receptor subtype in prostatic membrane particulates. Our data indicate that STZ-induced diabetes caused a variety of abnormalities including a down-regulation in the density of M3 muscarinic receptors in the rat prostate and that insulin, but not myo-inositol could prevent the development of these abnormalities.

Characterization of endothelin receptors in streptozotocin-induced diabetic rat vas deferens.

As there is increasing evidence that diabetes induces changes in the plasma levels of endothelins (ETs) and in the properties of ET receptors in peripheral tissues, and as there are reports indicating the presence of significant amounts of ET receptors in mammalian vasa deferentia, we studied possible alterations in ET receptor characteristics in the vasa deferentia of the following groups of rats: 8 weeks diabetic (D8), 8 weeks age-matched control (C8), 16 weeks diabetic (D16), 16 weeks diabetic-insulin-treated (started 8 weeks after the onset of diabetes) (DI16), and 16 weeks age-matched control (C16). Diabetes was induced by the i.v. injection of 65 mg/kg streptozotocin (STZ). Diabetic rats had hyperglycemia, hypoinsulinemia, glucosuria, polydipsia, and polyuria and had smaller vasa deferentia than control and diabetic-insulin-treated animals. Receptor binding experiments with [125I]ET-1 demonstrated that the densities of ET receptors in vasa deferentia from D8, C8, D16, DI16, and C16 animals were 377 +/- 11, 255 +/- 24, 315 +/- 18, 210 +/- 12, and 214 +/- 7 fmol/mg of protein, respectively. [125I]ET-1 binding to the ET receptors was inhibited by ET-1 (non-selective), BQ 610 (ETA selective), ET-3 (ETC selective), and IRL 1620 (ETB selective) with the following rank order of Ki values: ET-1 < BQ 610 < ET-3 < < IRL 1620. The pharmacological profile of the ET receptors was similar in all groups and was consistent with the predominance of the ETA receptor subtype in the rat vasa deferentia. Our data indicate that experimental diabetes up-regulates the density of ET receptors in the rat vasa deferentia and that the receptor up-regulation is reversed by insulin treatment.

Assessment of coronary artery patency with cine computed tomography in a dog model of occlusion-reperfusion.

RATIONALE AND OBJECTIVES: Determination of coronary artery patency may have therapeutic and prognostic significance particularly in the setting of acute myocardial infarction. Previous studies with cine computed tomography have demonstrated remarkable accuracy in the determination of coronary artery bypass graft patency. Recent improvements in resolution capability have afforded the potential for determination of native coronary artery patency. The accuracy of coronary artery patency determined by cine computed tomography is investigated in an animal model of coronary occlusion-reperfusion. METHODS: Seven anesthetized dogs were studied during control, coronary occlusion, and reperfusion conditions. Cine computed tomography was performed using electrocardiogram-triggered serial scans after intravenous injection of contrast medium. Coronary patency was determined by dye appearance in the epicardial artery coincident with its appearance in the left ventricular cavity. RESULTS: Patency was determined for the left anterior descending and left coronary arteries during three separate conditions in each dog, for a total of 42 patency determinations, and yielded the correct result in all cases. CONCLUSION: High-resolution cine computed tomography scanning can provide accurate determinations of coronary artery patency in an experimental model of occlusion-reperfusion.