l-Lysine Acts as a Serotonin Type 4 Receptor Antagonist to Counteract In Vitro and In Vivo the Stimulatory Effect of Serotonergic Agents on Aldosterone Secretion in Man.

In the normal human adrenal gland, serotonin (5-HT) stimulates aldosterone secretion through the 5-HT4 receptor (5-HT4R). However, the physiological role of the serotonergic control of adrenocortical function is not known. In the present study, we have investigated the ability of l-Lysine, which has been shown to act as a 5-HT4 receptor antagonist, to counteract in vitro and in vivo the stimulatory effect of 5-HT4R agonists on aldosterone production. l-Lysine was found to inhibit aldosterone production induced by 5-HT and the 5-HT4R agonists BIMU8 from cultured human adrenocortical cells. The action of l-Lysine (4.95 g/day orally) on the adrenal cortex was also evaluated in 20 healthy volunteers in a double blind, cross-over, placebo controlled study. l-Lysine had no significant influence on basal plasma aldosterone levels and the aldosterone responses to upright posture, tetracosactide, and low sodium diet (10 mmol/day for 3 days). Conversely, l-Lysine significantly reduced the surge of plasma aldosterone induced by metoclopramide indicating that l-Lysine is able to efficiently antagonize the adrenal 5-HT4 receptors in vivo. These results suggest that l-Lysine supplementation may represent a new treatment of primary adrenal diseases in which corticosteroid hypersecretion is driven by overexpressed 5-HT4 receptors.

A step towards cinacalcet testing for the diagnosis of primary hyperparathyroidism: comparison with the standardized intravenous calcium loading. A pilot study.

OBJECTIVE: A calcium load to suppress parathyroid hormone (PTH) secretion can help to perform the diagnosis in some case of primary hyperparathyroidism (PHPT) with atypical presentation. A similar test with calcimimetic, which avoids hypercalcaemia, would be of interest. Our proof of concept study was conducted to compare firstly the results of a single-dose cinacalcet testing with those of the standardized short-time calcium load in healthy control (HC) and secondly the results of the single-dose cinacalcet testing in HC and in PHPT. METHODS: Twelve HCs received in a random order, at a 2-week interval, either 0·33 mmol/kg calcium gluconate intravenously for 3 h, or a single oral dose of 30 mg or 60 mg cinacalcet. Twelve PHPTs received 30 mg cinacalcet and twelve other PHPTs 60 mg cinacalcet orally. Calcaemia and serum PTH levels were measured basally and then hourly for 6 h. RESULTS: In HC, plasma calcium did not significantly change after cinacalcet intake, whereas calcaemia rose up to 3·47 ± 0·05 mmol/l (mean ± SEM) at the end of the calcium load. PTH dropped from basal level to a similar extend (≥80%) with 60 mg cinacalcet and calcium load, whereas the decrease was significantly lesser (P < 0·01) with 30 mg cinacalcet. In PHPT, serum PTH levels dropped by 44·8 ± 6·9% and 58·2 ± 5·3% 1 h after the respective intake of 30 and 60 mg cinacalcet. One hour after the oral intake of 60 mg cinacalcet, serum PTH levels were <8 ng/l in HC and ≥8 ng/l in PHPT. CONCLUSION: Sixty milligrams of cinacalcet provides similar results as the standardized calcium load test; PHPT patients have a lower response to 60 mg cinacalcet than HC.

Abnormal Sensitivity to Glucagon and Related Peptides in Primary Adrenal Cushing's Syndrome.

Illegitimate G-protein coupled receptors are known to control cortisol secretion in adrenal adenomas and bilateral macronodular adrenal hyperplasias (BMAHs) causing Cushing's syndrome. In the present study, we have evaluated the role of glucagon in the regulation of cortisol secretion in 13 patients with BMAH or adrenocortical adenoma causing subclinical or overt Cushing's syndrome. Injection of glucagon provoked an increase in plasma cortisol in 2 patients. After surgery, immunohistochemical studies showed the presence of glucagon receptor-like immunoreactivity in clusters of spongiocytic cells in adrenal tissues from patients who were sensitive in vivo to glucagon. We also observed an in vitro cortisol response to vasoactive intestinal peptide from an adenoma, which was insensitive to glucagon and pituitary adenylate cyclase-activating peptide. Altogether, our data show that ectopic glucagon receptors are expressed in some adrenal cortisol-producing benign lesions. Our results also indicate that circulating glucagon may influence cortisol release under fasting conditions.

Study of the involvement of pancreastatin in the physiopathology of diabetes mellitus associated with nonsecreting pituitary adenomas.

Pancreastatin, derived from chromogranin A, inhibits insulin and stimulates glucagon secretion in rodents. Immunohistochemistry localised pancreastatin in human pancreatic islet cells and gonadotroph pituitary cells. Nonsecreting pituitary adenomas, frequently associated with diabetes mellitus, arise quasi-constantly from gonadotroph cells. We evaluated the possible involvement of pancreastatin in the physiopathology of diabetes mellitus associated with nonsecreting pituitary adenomas. Plasma pancreastatin levels were measured by radioimmunoassay in 5 groups of subjects: 10 patients with nonsecreting pituitary adenomas associated with diabetes mellitus (group I), 10 patients with nonsecreting pituitary adenomas without diabetes (Group II), 10 patients with ACTH or GH-secreting pituitary adenomas and diabetes mellitus (Group III), 10 diabetic patients without pituitary adenomas (Group IV), and 10 healthy controls (Group V). Kidney and liver functions were normal in all of them and no patient was treated with a proton pump inhibitor. All pituitary adenomas were trans-sphenoidally removed. Immunohistochemistry against pancreastatin was performed in 5 patients of each of the 3 groups of pituitary adenomas. Plasma pancreastatin levels were not different between the different groups: 182±46 pg/ml (Group I), 195±57 pg/ml (Group II), 239±42 pg/ml (Group III), 134±31 pg/ml, (Group IV), and 122±29 pg/ml (Group V). In contrast, they were significantly (p<0.05) higher before (391±65 pg/ml) than after trans-sphenoidal surgery (149±18 pg/ml) without post-surgical change in diabetes. An immunostaining against pancreastatin was found in a majority of pituitary adenomas, associated or not with diabetes mellitus. These results argue against a role of pancreastatin in the pathogenesis of diabetes mellitus associated with nonsecreting pituitary adenomas.

Short course of immune-suppressive doses of prednisolone, evaluated through a prospective double-masked placebo-controlled clinical trial in healthy Beagles, is associated with sustained modifications in renal, hydration, and electrolytic status.

OBJECTIVE: To investigate the effects and duration of orally administered prednisolone on renal function evaluated by glomerular filtration rate (GFR) determination and creatinine (Cr) and symmetric dimethylarginine (SDMA) concentrations as well as on urinalysis, electrolytes, and hydric status in healthy dogs. ANIMALS: 14 healthy Beagles. PROCEDURES: In this prospective double-masked placebo-controlled study, dogs were randomized after baseline evaluation to receive a 7-day course of either prednisolone (1.5 to 2.0 mg/kg, PO, q 12 h) or a placebo. A repeated-measure design was performed, each dog participating in 4 successive sampling sessions. Clinical data, systolic blood pressure, CBC, and biochemical analyses including serum SDMA concentration, GFR determination, urine output quantification, and complete urinalysis were performed for all dogs the day before (D0) and at the end of steroid administration (D7) as well as 2 weeks (D21) and 4 weeks (D35) after the end of treatment. RESULTS: At D7, when compared with baseline, GFR increased significantly in treated dogs, whereas creatinine and SDMA concentrations decreased significantly. GFR and Cr but not SDMA modifications persisted significantly at D21. None of the variables differed significantly from baseline at D35. The OR of presenting an albumin band on urine electrophoresis was 2.4 times as high in treated versus control dogs (OR, 36; 95% CI, 1.8 to 719.4; P = 0.02). CLINICAL RELEVANCE: A short-term course of immune-suppressive prednisolone treatment in healthy dogs leads to a sustained but reversible renal hyperfiltration state. Modification in electrolytic variables can affect the clinical interpretation of blood work in such patients.

Quantitative assessment of urea generation and elimination in healthy dogs and in dogs with chronic kidney disease.

BACKGROUND: Kinetic assessment of urea, the main end product of protein metabolism, could serve to assess protein catabolism in dogs with chronic kidney disease (CKD). Protein malnutrition and catabolism are poorly documented in CKD and they often are neglected clinically because of a lack of appropriate evaluation tools. HYPOTHESIS: Generation and excretion of urea are altered in dogs with CKD. ANIMALS: Nine dogs with spontaneous CKD (IRIS stages 2-4) and 5 healthy research dogs. METHODS: Endogenous renal clearance (Clrenal) of urea and creatinine was measured first. Exogenous plasma clearance (Clplasma, total body clearance) of the 2 markers then was determined by an IV infusion of urea (250-1,000 mg/kg over 20 minutes) and an IV bolus of creatinine (40 mg/kg). Extrarenal clearance (Clextra) was defined as the difference between Clplasma)and Clrenal. Endogenous urea generation was computed assuming steady-state conditions. RESULTS: Median Clrenal and Clextra of urea were 2.17 and 0.21 mL/min/kg in healthy dogs and 0.37 and 0.28 mL/min/kg in CKD dogs. The proportion of urea cleared by extrarenal route was markedly higher in dogs with glomerular filtration rate<1 mL/kg/min than in normal dogs, reaching up to 85% of the total clearance. A comparable pattern was observed for creatinine excretion, except in 1 dog, Clextra remained<20% of Clplasma. CONCLUSION: Extrarenal pathways of urea excretion are predominant in dogs with advanced CKD and justify exploring adjunctive therapies based on enteric nitrogen excretion in dogs. A trend toward increased urea generation may indicate increased catabolism in advanced CKD.

Breed dependency of reference intervals for plasma biochemical values in cats.

BACKGROUND: Reference intervals (RI) are pivotal in clinical pathology. The influence of breed on RI has been poorly documented in cats. HYPOTHESIS/OBJECTIVES: RI for plasma biochemistry variables are breed-dependent in cats. ANIMALS: Five hundred and thirty-six clinically healthy, fasted, client-owned cats from 4 breeds: Holly Birman (n=132), Chartreux (n=129), Maine Coon (n=139), and Persian (n=136). METHODS: Prospective observational study: Blood samples were collected from the cephalic vein into capillary tubes containing lithium heparin. Plasma glucose, urea, creatinine, total proteins, albumin, calcium, phosphate, sodium, potassium, chloride, and total CO2 concentrations and the activities of alanine aminotransferase and alkaline phosphatase were assayed with a dry slide biochemical analyzer. RI were defined as central 95% intervals bounded by the 2.5th and 97.5th percentiles. Data were analyzed by a linear mixed effects model with type I error rate of 0.05. RESULTS: A significant (P<.05) breed effect was observed for 9/13 variables. The magnitude of the differences between breeds could be clinically relevant for creatinine, glucose, and total protein. Age, body weight, sex, and housing conditions had significant (P<.05) breed-related effects on different variables. CONCLUSIONS AND CLINICAL IMPORTANCE: Breed-specific RI should be considered for cats.

Effect of experimental hypothyroidism on glomerular filtration rate and plasma creatinine concentration in dogs.

BACKGROUND: Hypothyroidism affects renal function in a manner opposite the effects of hyperthyroidism. OBJECTIVE: To evaluate the effects of experimentally induced hypothyroidism on glomerular filtration rate (GFR) and basal plasma creatinine concentration in dogs. ANIMALS: Sixteen anestrous, female dogs. METHODS: Hypothyroidism was induced by administration of (131)I in 8 dogs, and 8 healthy euthyroid dogs acted as controls. Exogenous plasma creatinine clearance (an estimate of GFR) was measured in all dogs before (control period) and 43-50 weeks after induction of hypothyroidism (posttreatment period). Other pharmacokinetic parameters of creatinine were also determined. RESULTS: No significant difference was observed for basal plasma creatinine concentration and creatinine clearance between control and hypothyroid dogs in the control period. In the posttreatment period, mean + or - SD creatinine clearance in the hypothyroid group (2.13 + or - 0.48 mL/min/kg) was lower (P < .001) than that of the control group (3.20 + or - 0.42 mL/kg/min). Nevertheless, basal plasma creatinine concentrations were not significantly different between the hypothyroid and control groups (0.74 + or - 0.18 versus 0.70 + or - 0.08 mg/dL, respectively) because endogenous production of creatinine was decreased in hypothyroid dogs (22 + or - 3 versus 32 + or - 5 mg/kg/d, P=.001). CONCLUSION AND CLINICAL IMPORTANCE: Hypothyroidism causes a substantial decrease in GFR without altering plasma creatinine concentrations, indicating that GFR evaluation is needed to identify renal dysfunction in such patients.

Effect of thyroxine supplementation on glomerular filtration rate in hypothyroid dogs.

BACKGROUND: Glomerular filtration rate (GFR) is decreased in humans with hypothyroidism, but information about kidney function in dogs with hypothyroidism is lacking. HYPOTHESIS: Hypothyroidism influences GFR in dogs. The objective of this study was to assess GFR in hypothyroid dogs before implementation of thyroxine supplementation and after re-establishing euthyroidism. ANIMALS: Fourteen hypothyroid dogs without abnormalities on renal ultrasound examination or urinalysis. METHODS: Blood pressure and GFR (measured by exogenous creatinine clearance) were measured before treatment (T0, n=14) and at 1 month (T1, n=14) and at 6 months (T6, n=11) after beginning levothyroxine supplementation therapy (20 microg/kg/d, PO). The response to therapy was monitored at T1 by measuring serum total thyroxine and thyroid stimulating hormone concentrations. If needed, levothyroxine dosage was adjusted and reassessed after 1 month. Statistical analysis was performed using a general linear model. Results are expressed as mean+/-standard deviation. RESULTS: At T0, the average age of dogs in the study group was 6.3+/-1.4 years. Their average body weight decreased from 35+/-18 kg at T0 to 27+/-14 kg at T6 (P<.05). All dogs remained normotensive throughout the study. GFR increased significantly with levothyroxine supplementation; the corresponding results were 1.6+/-0.4 mL/min/kg at T0, 2.1+/-0.4 at T1, and 2.0+/-0.4 at T6 (P<.01). CONCLUSION: GFR was <2 mL/min/kg in untreated hypothyroid dogs. Re-establishment of a euthyroid state increased GFR significantly.

Association of plasma N-terminal pro-B-type natriuretic peptide concentration with mitral regurgitation severity and outcome in dogs with asymptomatic degenerative mitral valve disease.

BACKGROUND: The clinical outcome of dogs affected by degenerative mitral valve disease (MVD) without overt clinical signs is still poorly defined, and criteria for identification of animals that are at a higher risk of early decompensation have not yet been determined. HYPOTHESIS: N-terminal pro-B-type natriuretic peptide plasma concentration (NT-proBNP) is correlated with mitral regurgitation (MR) severity and can predict disease progression in dogs with asymptomatic MVD. ANIMALS: Seventy-two dogs with asymptomatic MVD, with or without heart enlargement (International Small Animal Cardiac Health Council: ISACHC classes 1a and 1b), and a control group of 22 dogs were prospectively recruited. METHODS: Severity of MR was quantitatively assessed from the regurgitation fraction (RF) by the proximal isovelocity surface area method. Consequences of MR were evaluated from measurements of the left atrium/aorta ratio (LA/Ao), fractional shortening (FS), end-diastolic and end-systolic left ventricular volumes indexed to body surface area (EDVI and ESVI). The relevance of these echo-Doppler indices and NT-proBNP for prediction of outcome at 12 months was studied. RESULTS: A significant correlation was found between NT-proBNP and RF, LA/Ao, FS, and EDVI (P < .05). NT-proBNP was higher in dogs with MVD (ISACHC classes 1a and 1b) compared with the control group (P= .025 and < .001, respectively). The difference was not significant when only dogs from ISACHC class 1a with RF < 30% were considered. Lastly, NT-proBNP was higher in dogs that underwent MVD decompensation at 12 months (P < .05). CONCLUSIONS AND CLINICAL IMPORTANCE: NT-proBNP is correlated with MVD severity and prognosis in dogs with asymptomatic MVD.

Ectopic expression of serotonin7 receptors in an adrenocortical carcinoma co-secreting renin and cortisol.

Abnormal expression of membrane receptors has been previously described in benign adrenocortical neoplasms causing Cushing's syndrome. In particular, we have observed that, in some adreno corticotropic hormone (ACTH)-independent macronodular adrenal hyperplasia tissues, cortisol secretion is controlled by ectopic serotonin(7) (5-HT(7)) receptors. The objective of the present study was to investigate in vitro the effect of serotonin (5-hydroxy tryptamine; 5-HT) on cortisol and renin production by a left adrenocortical carcinoma removed from a 48-year-old female patient with severe Cushing's syndrome and elevated plasma renin levels. Tumor explants were obtained at surgery and processed for immunohistochemistry, in situ hybridization and cell culture studies. 5-HT-like immunoreactivity was observed in mast cells and steroidogenic cells disseminated in the tissue. 5-HT stimulated cortisol release by cultured cells. The stimulatory effect of 5-HT on cortisol secretion was suppressed by the 5-HT(7) receptor antagonist SB269970. In addition, immunohistochemistry showed the occurrence of 5-HT(7) receptor-like immunoreactivity in carcinoma cells. mRNAs encoding renin as well as renin-like immunoreactivity were detected in endothelial and tumor cells. Cell incubation studies revealed that the adrenocortical tissue also released renin. Renin production was inhibited by 5-HT but was not influenced by ACTH and angiotensin II (Ang II). In conclusion, the present report provides the first demonstration of ectopic serotonin receptors, i.e. 5-HT(7) receptors, in an adrenocortical carcinoma. Our results also indicate that 5-HT can influence the secretory activity of malignant adrenocortical tumors in an autocrine/paracrine manner. The effects of 5-HT on adrenocortical tumor cells included a paradoxical inhibitory action on renin production and a stimulatory action on cortisol secretion involving 5-HT(7) receptors.

Plasma clearance of exogenous creatinine, exo-iohexol, and endo-iohexol in hyperthyroid cats before and after treatment with radioiodine.

BACKGROUND: Glomerular filtration rate (GFR) can be measured by clearance methods of different markers showing discrepancies and different reproducibility in healthy cats. Studies comparing different methods of GFR measurement in hyperthyroid cats have not yet been performed. HYPOTHESIS: Plasma clearance of exogenous creatinine (PECCT), exo-iohexol (PexICT), and endo-iohexol (PenICT) could lead to differences in GFR measurement and the need to use the same clearance method when comparing GFR before and after radioiodine treatment in hyperthyroid cats. ANIMALS: Fifteen client-owned hyperthyroid cats. METHODS: GFR was measured 1 day before and 1, 4, 12, and 24 weeks after treatment. Intravenous injection of iohexol was followed immediately by IV injection of creatinine. Plasma creatinine was measured by an enzymatic method. Plasma endo- and exo-iohexol were measured by high-performance liquid chromatography coupled to ultraviolet detection. RESULTS: Globally, the 3 GFR methods resulted in significantly different (P < .001) GFR results. GFR results among the different methods were the same (P= .999) at all time points. All 3 techniques indicated decreasing GFR after (131)I treatment. For each GFR technique, a significant decrease in GFR was observed between time point 0 and all other time points. This decrease stabilized 4 weeks after treatment, with very little decline afterward. CONCLUSION AND CLINICAL IMPORTANCE: It is mandatory to use the same GFR technique in follow-up studies. GFR testing at 4 weeks posttreatment could allow assessment of the final renal functional loss after treatment in hyperthyroid cats.

Effect of benazepril on survival and cardiac events in dogs with asymptomatic mitral valve disease: a retrospective study of 141 cases.

BACKGROUND: Angiotensin-converting enzyme inhibitors (ACEIs) improve quality of life and extend the life span of dogs with naturally acquired ISACHC class II-III congestive heart failure (CHF). However, their effects on asymptomatic heart disease remain controversial. HYPOTHESIS: Benazepril (BNZ), an ACEI, could have beneficial effects at the asymptomatic stage of degenerative mitral valve disease (MVD). ANIMALS: Dogs with ISACHC class Ia MVD and moderate-to-severe mitral regurgitation (MR) assessed by the color Doppler mapping technique at entry (Day 0) were retrospectively included. METHODS: Dogs were assigned to the treated group (BNZ group) if they received BNZ (and no other cardiac medication) from Day 0 or to the untreated group (UT group) if they did not receive any cardioactive treatment until occurrence of CHF. RESULTS: A total of 141 dogs were included in the study, 66 in the BNZ group (dosage: 0.30 +/- 0.13 mg/kg) and 75 in the UT group. In the population (n = 93) including all breeds except Cavalier (CKC) and King Charles Spaniels (KC), median survival time to all causes of death in the BNZ group (n = 34, 3.3 years) was significantly longer than in the UT group (n = 59, 1.9 years) as was time to cardiac event (P < .05). Conversely, no effect of the BNZ treatment was observed in the CKC and KC population. CONCLUSIONS AND CLINICAL RELEVANCE: BNZ had beneficial effects in asymptomatic dogs other than CKC and KC affected by MVD with moderate-to-severe MR. Breed distribution should be taken into account for interpretation of clinical trials performed in dogs with cardiac disease.

Exploration and management of adrenal incidentalomas. French Society of Endocrinology Consensus.

The French Society of Endocrinology convened a multidisciplinary panel of endocrinologists, radiologists, nuclear physicians and surgeons to address the appropriate evaluation and treatment of adrenal incidentalomas. The panel conducted a systematic review of medical literature on the following issues: epidemiology, natural history, radiological and scintigraphic evaluation, endocrine assessment, surgical management and appropriate follow-up. The following text reports the recommendations of experts on behalf of the French Society of Endocrinology. The authors emphasize the paucity of published scientific data that hampers evidence-based medicine recommendations. The crucial points of the French consensus are: the usefulness of CT-scanning evaluation of adrenal incidentalomas, the systematic screening for pheochromocytoma, the usefulness of the 1mg overnight dexamethasone test to screen for latent hypercortisolism, the difficulty to interpret mild biological abnormalities of the HPA axis, the consensus to remove surgically most of tumours greater than 4cm, the necessity to follow clinically glucorticoid tissular targets in the follow-up of non operated benign adrenocortical incidentalomas.

Familial adrenocorticotropin-independent macronodular adrenal hyperplasia with aberrant serotonin and vasopressin adrenal receptors.

ACTH-independent macronodular adrenocortical hyperplasia (AIMAH) is rare and generally presents as a sporadic disease. We describe a familial case of AIMAH with in vivo and in vitro demonstration of aberrant 5-HT4 and vasopressin adrenal receptors. Two sisters presented with clinical and biological features of mild Cushing's syndrome with bilateral macronodular adrenal enlargement on computerized tomography (CT)-scan evaluation. In vivo pharmacological tests showed a significant increase in plasma cortisol after terlipressin and metoclopramide administration. Unilateral adrenalectomy was performed in one of these patients. Reverse transcriptase-PCR analysis of the hyperplastic tissue revealed expression of 5-HT4 receptor isoforms (a), (b), (c), (i), and (n), and of vasopressin receptors, V1 and V2. Their father and brother were overweight, had easy bruisability and presented with biological features of subclinical Cushing's syndrome. CT scan showed moderate adrenal enlargement. In vivo pharmacological screening tests for the detection of adrenal aberrant receptors in the brother were negative. Finally, three out of the two sisters' children were evaluated. They had neither clinical nor biological features of Cushing's syndrome. Their adrenal glands were normal on CT-scan evaluation. In vivo evaluation for the detection of aberrant adrenocortical receptors performed in one of these subjects was negative. In conclusion, this study shows that (i) familial AIMAH could be an autosomal dominantly inherited disorder; (ii) aberrant 5-HT4 serotonin and vasopressin receptors can be expressed in familial AIMAH; and (iii) phenotypic expression of familial AIMAH could be varied in a same family and more pronounced in female than in male patients.

Comparison and reproducibility of plasma clearance of exogenous creatinine, exo-iohexol, endo-iohexol, and 51Cr-EDTA in young adult and aged healthy cats.

BACKGROUND: Important characteristics determining the usefulness of a method for glomerular filtration rate (GFR) measurement are convenience, availability, and reproducibility. HYPOTHESIS: The use of different plasma clearance methods could lead to different results and differences in reproducibility. ANIMALS: Twelve healthy cats: 6 young adult cats (age 7-12 months), and 6 aged cats (age 9-12 years) were included in this study. METHODS: A cross-over design was used to compare the plasma clearance of exogenous creatinine (PECCT), exo-iohexol (PexICT), endo-iohexol (PenICT), and chromium-51 ethylenediaminetetraacetic acid (51Cr-EDTA), and to investigate reproducibility of these methods. Cats of different ages were included to determine if differences in GFR in young adult versus aged cats would be detected with these methods. The PECCT, PexICT, and PenICT were performed in a combined manner. Plasma data were subjected to noncompartmental (creatinine, exo-iohexol, and endo-iohexol) or bicompartmental (51Cr-EDTA) analysis with a statistical moment approach. Area under the concentration-time curve was calculated using the trapezoidal rule with extrapolation to infinity. Statistical analyses were carried out using a random effects model. RESULTS: Globally, the 4 methods differed significantly (P < .0001) in GFR assessment. Clearance of exo-iohexol and chromium-51 ethylenediaminetetraacetic acid (51Cr -EDTA) showed the highest and lowest reproducibility, respectively. Only plasma clearance of creatinine differed significantly between young adult and aged cats. CONCLUSION AND CLINICAL IMPORTANCE: We found considerable differences in reproducibility of different GFR measurements. These findings should be taken into account not only in practice but also in future studies involving GFR measurement.

Time course of COX-1 and COX-2 expression during ischemia-reperfusion in rat skeletal muscle.

The aim of this study was to assess cyclooxygenase (COX)-1 and COX-2 expression in skeletal muscle after an ischemia-reperfusion (I/R). Male Sprague-Dawley rats were subjected to unilateral hindlimb ischemia for 2 h and then euthanized after 0, 1, 2, 4, 6, 10, 24, and 72 h of reperfusion. The COX protein and mRNA were assessed in control and injured gastrocnemius muscle. Muscle damage was indirectly determined by plasma creatine kinase activity and edema by weighing wet muscle. Creatine kinase activity in plasma increased as early as 1 h after reperfusion and returned to control levels by 72 h of reperfusion. Edema was observed at 6 and 10 h of reperfusion, but histological investigations showed an absence of tissular inflammatory cell infiltration. COX-1 mRNA was expressed in control muscle and was increased at 72 h of reperfusion, but the levels of associated COX-1 protein detected in control and injured gastrocnemius muscle were similar. COX-2 mRNA was not, or only slightly, detectable in control muscle and after I/R. In contrast, I/R induced major overexpression of COX-2 immunoreactivity at 6 and 10 h of reperfusion with a maximum at 10 h, whereas COX-2 protein was undetectable in control muscle. In conclusion, hindlimb I/R induced a large overexpression of COX-2 but not COX-1 protein between 6 and 10 h after injury. These results suggest a role for COX-2 enzyme in such pathophysiological conditions of the skeletal muscle.

Evaluation of Cystatin C for the Detection of Chronic Kidney Disease in Cats.

BACKGROUND: Serum cystatin C (sCysC) and urinary cystatin C (uCysC) are potential biomarkers for early detection of chronic kidney disease (CKD) in cats. An in-depth clinical validation is required. OBJECTIVES: To evaluate CysC as a marker for CKD in cats and to compare assay performance of the turbidimetric assay (PETIA) with the previously validated nephelometric assay (PENIA). ANIMALS: Ninety cats were included: 49 CKD and 41 healthy cats. METHODS: Serum CysC and uCysC concentrations were prospectively evaluated in cats with CKD and healthy cats. Based on plasma exo-iohexol clearance test (PexICT), sCysC was evaluated to distinguish normal, borderline, and low GFR. Sensitivity and specificity to detect PexICT < 1.7 mL/min/kg were calculated. Serum CysC results of PENIA and PETIA were correlated with GFR. Statistical analysis was performed using general linear modeling. RESULTS: Cats with CKD had significantly higher mean ± SD sCysC (1.4 ± 0.5 mg/L) (P < .001) and uCysC/urinary creatinine (uCr) (291 ± 411 mg/mol) (P < .001) compared to healthy cats (sCysC 1.0 ± 0.3 and uCysC/uCr 0.32 ± 0.97). UCysC was detected in 35/49 CKD cats. R(2) values between GFR and sCysC or sCr were 0.39 and 0.71, respectively (sCysC or sCr = µ + GFR + Îµ). Sensitivity and specificity were 22 and 100% for sCysC and 83 and 93% for sCr. Serum CysC could not distinguish healthy from CKD cats, nor normal from borderline or low GFR, in contrast with sCr. CONCLUSION: Serum CysC is not a reliable marker of reduced GFR in cats and uCysC could not be detected in all CKD cats.

Quantitative evaluation of renal function in healthy Beagle puppies and mature dogs.

Daily urinary collection and assessment of glomerular filtration rate (GFR) and effective renal plasma flow were performed in ten 2-month-old Beagle puppies and ten 6-9 year-old Beagle dogs to identify age-associated differences in renal function. The most striking differences in puppies compared to mature dogs were a higher daily urinary volume (+65%), GFR (+87%), free water reabsorption (+159%), a lower daily protein excretion (-88%), and fractional excretion of phosphorus (-35%). Renal function in Beagle puppies, but not mature dogs, was also quite different compared to data published in younger adult dogs.

Paracrine control of steroidogenesis by serotonin in adrenocortical neoplasms.

Serotonin (5-hydroxytryptamine; 5-HT) is able to activate the hypothalamo-pituitary-adrenal axis via multiple actions at different levels. In the human adrenal gland, 5-HT, released by subcapsular mast cells, stimulates corticosteroid production through a paracrine mode of communication which involves 5-HT receptor type 4 (5-HT4) primarily located in zona glomerulosa. As a result, 5-HT is much more efficient to stimulate aldosterone secretion than cortisol release in vitro and administration of 5-HT4 receptor agonists to healthy individuals is followed by an increase in plasma aldosterone levels without any change in plasma cortisol concentrations. Interestingly, adrenocortical hyperplasias and tumors responsible for corticosteroid hypersecretion exhibit various cellular and molecular defects which tend to reinforce the intraadrenal serotonergic tone. These pathophysiological mechanisms, which are summarized in the present review, include an increase in adrenal 5-HT production and overexpression of 5-HT receptors in adrenal neoplastic tissues. Altogether, these data support the concept of adrenal serotonergic paracrinopathy and suggest that 5-HT and its receptors may constitute valuable targets for pharmacological treatments of primary adrenal diseases.