Levels of insulin-like growth factor I (IGF-I) and IGF binding proteins 2 and 3 in serial postoperative serum samples and risk of prostate cancer recurrence.

OBJECTIVES: To determine changes of insulin-like growth factor I (IGF-I), IGF binding protein-2 (IGFBP-2), and IGFBP-3 levels in serial postoperative serum samples from prostate cancer patients with and without relapse and to evaluate the prognostic value of these molecules in the recurrence of prostate cancer. METHODS: From a group of patients with prostate cancer who had been followed for disease recurrence for almost 5 years after radical prostatectomy, we selected 38 patients (cases) who developed recurrent disease and 40 patients (controls) who were in remission. Of these patients, 70 had 4 and 8 had 3 serial postoperative serum samples collected. The median times for serum collection after surgery were 1.5 years for the first serial samples, 2.6 years for the second, 3.5 years for the third, and 4.5 years for the fourth. Serum levels of IGFBP-2, IGFBP-3, and IGF-I were measured, using commercial immunoassay kits. RESULTS: The study showed lower serum levels of IGFBP-2 and IGFBP-3 in the cases than in controls(P <0.05) but no difference in IGF-I levels between the two groups (P = 0.277). In the sequential samples, IGFBP-2 levels increased over time in the controls (P = 0.014) but did not change in the cases (P = 0.528). There were no increasing or decreasing trends for IGF-I and IGFBP-3 in either case or control group(P >0.05). CONCLUSIONS: The study suggests that IGFBP-2 may play a role in the progression of prostate cancer, but serum levels of IGFBP-2 as well as IGF-I and IGFBP-3 have no predictive values in the prognosis of prostate cancer.

Growth hormone stimulation testing in both short and normal statured children: use of an immunofunctional assay.

Accurate interpretation of the results of GH stimulation tests is of pivotal importance not only in the evaluation of the etiology of growth retardation in children but also in the selection of the best candidates for GH therapy. We performed this study to test a novel immunofunctional GH ( IFGH) assay that makes use of the concept that one GH molecule dimerizes two GH receptors and compared the results with those obtained using two GH assays, the Diagnostic Systems Laboratories ELISA and a Hybritech immunoradiometric assay in 19 children with short stature undergoing routine GH stimulation testing. We also tested 13 normally statured control children to revisit the issue of what constitutes normal GH responses to stimuli, using all three assays and arginine and either L-dopa or insulin-induced hypoglycemia as secretagogues. Concentrations of IGF-I, IGF binding protein-3, and acid labile subunit were measured as well. There was a significant correlation between peak IFGH and Diagnostic Systems Laboratories ELISA GH responses to stimuli (r(2) = 0.93) as well as between the Diagnostic Systems Laboratories ELISA and Hybritech immunoradiometric assay (r(2) = 0.91). There were no significant differences between the short stature and normal group in peak or mean GH concentrations regardless of the assay used; however, the IGF-I, IGF binding protein-3, and acid labile subunit concentrations were substantially lower in the short stature group. There was a wide spectrum of GH concentrations in the normal group; approximately 50% of the children had peak GH concentrations <7 ng/mL, approximately 30% <5 ng/mL, and two pubertal normal subjects peaked to only 2 ng/mL with use of both the ELISA and IFGH assays. We conclude that 1) sensitive GH assays, ELISA and immunoradiometric assay, accurately detect a GH capable of generating a biologic signal comparable to an IFGH and 2) that normal GH stimulation test results can be substantially lower than previously accepted. GH-dependent growth factors may be more sensitive indicators of GH sufficiency than GH concentrations in response to pharmacologic stimuli.

Insulin-like growth factors (IGF-I, free IGF-I and IGF-II) and insulin-like growth factor binding proteins (IGFBP-2, IGFBP-3, IGFBP-6, and ALS) in blood circulation.

Insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) play an important role in cell growth and differentiation. Clinical and epidemiological studies have indicated that measuring IGFs and IGFBPs in blood has potential implications in assessing growth-related abnormalities and risks of certain types of cancer. To facilitate the application, we reported a large collection of reference ranges of IGFs and IGFBPs in normal population and evaluations of these molecules in serum and plasma as well as the impact of freeze-thaw cycles on the measurement. IGF-I, IGFBP-3 andALS showed a similar pattern of change associated with age. Levels of these molecules were low at birth and increased with age through puberty. After puberty the levels declined slowly with age. Overall, IGF-I, IGFBP-3 and ALS were slightly higher in females than in males. Free IGF-I accounted for about 1% of the total IGF-I and its variation with age was similar to total IGF-I. IGF-II levels were also increased with age from birth to puberty, but became stable after puberty. There was little difference in IGF-II levels between genders. IGFBP-2 levels declined with age from birth to puberty. Levels of IGFBP-6 in contrast were increased with age. These IGF binding proteins were higher in males than in females. IGFs, IGFBP-3 and ALS were 5-10% higher in serum than in plasma. IGFBP-2 and IGFBP-6 differed substantially between serum and plasma. Freeze-thaw treatment up to five cycles had little impact on plasma levels of IGFs and IGFBP-3. Our observations suggest that levels of IGFs and their binding proteins are varied with age, gender, and types of specimen and that these variations need to be taken into consideration when IGFs and their binding proteins are utilized in clinic and research.

FK506 trough levels in whole blood and plasma in liver transplant recipients. Correlation with clinical events and side effects.

FK506 trough levels were measured by ELISA in paired whole-blood and plasma samples in 59 liver transplant recipients. Patients with nephrotoxicity had higher FK506 whole-blood and plasma levels (27.5 +/- 3.2 ng/ml and 1.44 +/- 0.14 ng/ml) than patients with stable liver function (15.2 +/- 2.1 ng/ml and 0.98 +/- 0.15 ng/ml, P < 0.05 and P < 0.01, respectively). Patients with acute rejection had FK506 whole-blood and plasma levels within the same range as patients with stable liver function. Patients with severe neurotoxicity had significantly higher FK506 whole-blood and plasma levels (31.3 +/- 6.8 ng/ml and 3.9 +/- 1.4 ng/ml) in comparison with patients with mild-to-moderate neurotoxicity (18.1 +/- 2.4 ng/ml and 1.1 +/- 0.13 ng/ml) (P = 0.048 and P < 0.001, respectively). Long-term use of FK506 was associated with a significant reduction in glomerular filtration rate at 1-year posttransplant in patients on primary FK506 treatment (33%, P < 0.001). The reduction in glomerular filtration rate correlated with the yearly mean FK506 plasma but not with whole-blood levels or FK506 dose. There was a correlation between FK506 whole-blood and plasma levels (r = 0.713, P < 0.001) but not between the levels (whole blood or plasma) and FK506 dose (mg/day or mg/kg/day). The mean FK506 whole-blood and plasma levels were 14.1 +/- 0.26 ng/ml and 0.96 +/- 0.75 ng/ml, respectively. There was a large intra- and interpatient variability in the ratio between whole-blood and plasma levels (range 1.0-73.5), with a mean ratio of 18.0 +/- 0.28 (+/- SEM). In conclusion, monitoring of FK506 trough levels is of importance to avoid nephro- and neurotoxicity, but monitoring is only of limited help to avoid acute rejection. Monitoring of FK506 levels in plasma seems to be superior to that in whole blood.

Alpha 1-antitrypsin excretion in stool in normal subjects and in patients with gastrointestinal disorders.

Fecal clearance of plasma alpha 1-antitrypsin is used as a measure of protein leakage into the intestinal tract. In this study, the alpha 1-antitrypsin concentration in stool and the plasma clearance of alpha 1-antitrypsin in normal subjects and in a consecutive series of patients with chronic diarrhea, malabsorption, or unexplained hypoalbuminemia was determined. The normal subjects were studied in their usual state and also when they had diarrhea secondary to ingestion of lactulose, sorbitol, sodium sulfate, or phenolphthalein. The study first concluded that induced diarrhea can cause an increase in alpha 1-antitrypsin clearance; if this is not considered in establishing normal values, there may be an overdiagnosis of excess protein leakage in patients with diarrhea. Second, there is a highly significant statistical correlation (P less than 0.001) between alpha 1-antitrypsin clearance and serum albumin concentration. On average, the serum albumin falls below 3.0 g/dL (30 g/L) when the alpha 1-antitrypsin clearance exceeds 180 mL/day, a value that is about threefold higher than the upper limit of normal. Third, three of nine patients with microscopic/collagenous colitis had elevated clearance of alpha 1-antitrypsin; by contrast, abnormal alpha 1-antitrypsin clearance was not found in 23 patients with idiopathic secretory diarrhea. Fourth, fecal alpha 1-antitrypsin concentration is not a reliable index of abnormal alpha 1-antitrypsin clearance.

Reduction of dietary phosphorus absorption by phosphorus binders. A theoretical, in vitro, and in vivo study.

Antacids used to decrease phosphorus absorption in patients with renal failure may be toxic. To find more efficient or less toxic binders, a three-part study was conducted. First, theoretical calculations showed that phosphorus binding occurs in the following order of avidity: Al3+ greater than H+ greater than Ca2+ greater than Mg2+. In the presence of acid (as in the stomach), aluminum can therefore bind phosphorus better than calcium or magnesium. Second, in vitro studies showed that the time required to reach equilibrium varied from 10 min to 3 wk among different compounds, depending upon solubility in acid and neutral solutions. Third, the relative order of effectiveness of binders in vivo was accurately predicted from theoretical and in vitro results; specifically, calcium acetate and aluminum carbonate gel were superior to calcium carbonate or calcium citrate in inhibiting dietary phosphorus absorption in normal subjects. We concluded that: (a) inhibition of phosphorus absorption by binders involves a complex interplay between chemical reactions and ion transport processes in the stomach and small intestine; (b) theoretical and in vitro studies can identify potentially better in vivo phosphorus binders; and (c) calcium acetate, not previously used for medical purposes, is approximately as efficient as aluminum carbonate gel and more efficient as a phosphorus binder than other currently used calcium salts.

Calcium absorption: effect of meal and glucose polymer.

Various nonelectrolyte meal components such as glucose and lysine enhance gastrointestinal calcium absorption under experimental conditions. The effect of a mixed meal on Ca absorption from Ca supplements is unknown. The effect of glucose polymer on Ca absorption when ingested with food also is unknown. Using a single-day method, we measured net Ca absorption from Ca carbonate when ingested in fasting state, with a steak and potatoes meal, and with the meal and 50 g glucose polymer. Eight healthy human subjects were studied after a 500-mg elemental Ca dose. Mean net Ca absorption was 195 +/- 18 mg (4.87 +/- 0.45 mmol) fasting, 213 +/- 21 mg (5.31 +/- 0.52 mmol) with a meal, and 179 +/- 16 mg (4.47 +/- 0.40 mmol) with a meal plus glucose polymer. The differences are not statistically significant. In normal people Ca absorption from Ca carbonate was not significantly enhanced by a meal or by 50 g glucose polymer ingested with food.

Gastrointestinal absorption of calcium from milk and calcium salts.

Whether ingested calcium is absorbed more efficiently from freely water-soluble calcium salts than from poorly soluble salts is unclear. It is also unknown whether calcium is absorbed better from dairy products than from calcium salts. Using a method by which the net absorption of calcium can be accurately measured after a single dose, we studied eight healthy fasting subjects after they took a 500-mg dose of calcium from each of five calcium salts with various degrees of water solubility and from milk. The order of administration of the agents given was randomly determined. The mean (+/- SEM) net calcium absorption, in decreasing order of the solubility of the salts, was 32 +/- 4 percent from calcium acetate, 32 +/- 4 percent from calcium lactate, 27 +/- 3 percent from calcium gluconate, 30 +/- 3 percent from calcium citrate, and 39 +/- 3 percent from calcium carbonate. The differences in absorption were not statistically significant according to analysis of variance. On the basis of in vitro solubility experiments in acid mediums, we hypothesize that acid dissolution in the gastrointestinal tract may be responsible for the similar absorption of calcium from salts with widely different water solubilities. Calcium absorption from whole milk (31 +/- 3 percent) was similar to absorption from calcium salts. We conclude that calcium absorption from carbonate, acetate, lactate, gluconate, and citrate salts of calcium, and from whole milk, is similar in fasting healthy young subjects. Further study will be required to determine whether the results would be different in older subjects, with a higher dose of calcium, or if the calcium was ingested with food.

The preservation of urine samples for determination of renal stone risk factors.

A preservation technique for urine specimens before determination of stone risk factors was evaluated. The purpose of these experiments was to prove the effectiveness of the preservatives used to prevent changes in the concentrations of those constituents measured. Measured concentrations in fresh specimens were compared with those in the same specimens after storage with the preservatives. Refrigeration at 4 degrees C up to five days was appropriate in a laboratory setting, as no significant changes in urinary concentrations occurred. Refrigeration, however, did not offer a convenient method for shipping. Chemical preservation was found to be an effective alternative to refrigeration. Thymol prevented changes in concentration of pH, citrate, uric acid, sulfate, sodium, potassium, and cyclic AMP, while a mixture of hydrochloric (HCl) acid and boric acid prevented changes in calcium, magnesium, phosphorus, oxalate, ammonium, and creatinine. Thus, the addition of thymol or HCl/boric acid to urine specimens will prevent significant changes in the concentrations of stone risk factors.

Inhibition by citrate of spontaneous precipitation of calcium oxalate in vitro.

Effect of citrate on the spontaneous precipitation of calcium oxalate was examined in synthetic media. Citrate significantly increased the formation product of calcium oxalate. This "direct" measure of inhibitor activity, representing activity product at the point of nucleation, rose by 76% by the addition of citrate sufficient to provide trivalent citrate concentration of 1.49 mM. Moreover, citrate inhibited calcium oxalate crystallization by complexing calcium and lowering calcium oxalate saturation. This "indirect" measure of inhibitor activity was assessed from the concentration product of calcium oxalate at the point of nucleation, since this measure should provide a reflection of both ion pair formation and direct inhibitor activity of citrate. The concentration product exceeded the formation product at all ionic (trivalent) citrate concentrations, particularly at high ionic citrate levels. At the ionic citrate concentration of 1.49 mM, the rise in the concentration product was 373%, which was nearly fivefold that observed for the formation product. The presence of ferric or aluminum cations at a physiologic concentration of 2 mg/l did not modify the increase in formation product produced by citrate. Thus, citrate inhibits calcium oxalate crystallization, largely by complexing citrate, but also by directly affecting nucleation. Presence of ferric or aluminum cations at a physiological concentration does not modify the inhibitor action of citrate.

The effects of ryanodine on passive calcium fluxes across sarcoplasmic reticulum membranes.

Ryanodine at concentrations of 0.01-10 microM increased, while greater concentrations of 10-300 microM decreased the calcium permeability of both rabbit fast twitch skeletal muscle junctional and canine cardiac sarcoplasmic reticulum membranes. Ryanodine did not alter calcium binding by either sarcoplasmic reticulum membranes or the calcium binding protein, calsequestrin. Therefore, the effects by this agent appear to involve only changes in membrane permeability, and the characteristics of the calcium permeability pathway affected by ryanodine were those of the calcium release channel. Consistent with this, the actions by ryanodine were localized to junctional sarcoplasmic reticulum membranes and were not observed with either longitudinal sarcoplasmic reticulum or transverse tubular membranes. In addition, passage of the junctional sarcoplasmic reticulum membranes through a French press did not diminish the effects of ryanodine indicating that intact triads were not required. Under the conditions used for the permeability studies, the binding of [3H]ryanodine to skeletal junctional sarcoplasmic reticulum membranes was specific and saturable, and Scatchard analyses indicated the presence of a single binding site with a Kd of 150-200 nM and a maximum capacity of 10.1-18.9 pmol/mg protein. [3H]ryanodine binding to this site and the increase in membrane calcium permeability caused by low concentrations of ryanodine had similar characteristics suggesting that actions at this site produce this effect. Depending on the assay conditions used, ryanodine (100-300 microM) could either increase or decrease ATP-dependent calcium accumulation by skeletal muscle junctional sarcoplasmic reticulum membranes indicating that the alterations of sarcoplasmic reticulum membrane calcium permeability caused by this agent can be determined in part by the experimental environment.

The effect of pulsed electromagnetic fields on the corrosion of a chromium-cobalt-nickel alloy orthopaedic implant.

In order to assess whether pulsed electromagnetic fields influence the rate of corrosion of orthopaedic metal implants, an alloy, called MP-35N, was exposed for 3 wk to a pulsed electromagnetic field. The results demonstrated that while there was a progressive release of the major constituents of MP-35N, i.e. cobalt (32.5%), nickel (36%), and chromium (20%), with time, corrosion was not significantly higher in the presence of the pulsed electromagnetic field when compared to that of the non-exposed pins. There was a significantly higher release of cobalt by the control pins after 5, 10, and 15 d incubation when compared with the pulsed pins. These findings were confirmed by SEM which demonstrated progressive surface corrosion with time and that the extent of corrosion was similar for both the control and pulsed pins. These results suggest that pulsed electromagnetic fields have no effect in promoting the surface corrosion of orthopaedic metallic implants.

Altered calcium homeostasis in Dahl hypertensive rats: physiological and biochemical studies.

Abnormal calcium (Ca) homeostasis has been reported in essential hypertension and in the Okamoto-Aoki strain of spontaneously hypertensive rats. These abnormalities include increased urinary excretion of calcium and decreased ionized serum calcium (Ca2+). To pursue these abnormalities we studied the chronology of urinary excretion of electrolytes in a genetically homogeneous strain of hypertensive rat, the Dahl/Rapp salt sensitive (S) and resistant (R) rat (at ages 3, 5, 7, 9, 12, 20 and 32 weeks). We also characterized the renal adenylate cyclase-cAMP system by measuring urinary cAMP excretion and adenylate cyclase response to membrane receptor agonists in renal membranes from S and R rats at day 2 and at 6 and 28 weeks of age. Urinary calcium excretion was higher in S than in R at 3, 5 and 7 weeks (0.48 +/- 0.04 versus 0.24 +/- 0.01 mg/mg creatinine at 7 weeks, P less than 0.01). Sodium and phosphorous excretion were lower in S than in R rats at 5, 7, 9, and 12 weeks, and at 5, 7, 9, 12, 20 and 32 weeks, respectively. Potassium excretion was similar in the two groups. Plasma ionized calcium was lower in S than in R rats (3.9 +/- 0.1 versus 4.5 +/- 0.1 mg/dl, P less than 0.01) only at 7 weeks of age. Plasma parathyroid hormone (PTH) was not different between S and R rats. Cyclic AMP excretion and the renal adenylate cyclase response to PTH when referenced to basal activity was lower in S than in R rats at all ages.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary response to oral potassium citrate therapy for urolithiasis in a private practice setting.

Oral potassium citrate therapy was recently approved for treatment of urolithiasis based on results of experiments in a university research setting. However, no supporting studies from private practice have been published. The present study was undertaken to assess the response to one week of oral potassium citrate therapy (60 mEq/day), with respect to urinary risk factors for kidney stones, in a private practice setting. A significant rise in urinary pH, citrate, and potassium excretion, accompanying a significant fall in calcium excretion, were observed. Urinary saturation of calcium oxalate was significantly reduced, as some risk factors in urolithiasis were corrected with oral potassium citrate therapy. The response to therapy in private practice was comparable to that observed in a university research setting.

Exaggerated natriuretic and calciuric responses to hydrochlorothiazide in renal hypercalciuria but not in absorptive hypercalciuria.

Patients with hypercalciuria have been reported to have an exaggerated response to hydrochlorothiazide (HCTZ), implying a renal tubular defect in solute reabsorption. To determine whether this disturbance is generalized or unique to a particular pathogenetic type of hypercalciuria, we measured the increments in urinary sodium (delta Na), calcium (delta Ca), and magnesium after a 100-mg dose of oral HCTZ in 10 normal subjects and 31 patients with different types of hypercalciuric nephrolithiasis. Eleven patients with renal hypercalciuria had significantly greater delta Na (P less than 0.005) and delta Ca (P less than 0.005) than the normal subjects. Ten patients with absorptive hypercalciuria and 10 patients with fasting hypercalciuria without parathyroid stimulation had delta Na and delta Ca indistinguishable from those of normal subjects. In all groups, urinary HCTZ and basal 24-h urinary Na did not differ. The results suggest that the unique natriuretic and calciuric responses to HCTZ occur only in renal hypercalciuric patients with secondary hyperparathyroidism. The data support a renal tubular defect in renal hypercalciuric in contrast to other diagnostic categories of hypercalciuric nephrolithiasis.

Postmenopausal osteoporosis as a manifestation of renal hypercalciuria with secondary hyperparathyroidism.

An apparently unique presentation of osteoporosis was encountered in eight postmenopausal women (mean age, 56.8 yr). They had renal hypercalciuria, since they had fasting hypercalciuria [0.17 +/- 0.04 (+/- SD) mg/100 ml glomerular filtrate (GF)] in the setting of normocalcemia and parathyroid stimulation (high serum immunoreactive PTH and/or urinary cAMP). Serum 1,25-dihydroxyvitamin D was not significantly different (28 +/- 7 vs. 34 +/- 2 pg/ml) from that in a nonelderly control group, but fractional intestinal calcium (Ca) absorption was significantly lower (0.382 +/- 0.123 vs. 0.49 +/- 0.06; P less than 0.025). Thus, the patients did not have compensatory intestinal hyperabsorption of Ca despite PTH excess. Treatment with hydrochlorothiazide (50 mg/day) produced a decline in fasting urinary Ca (to 0.07 +/- 0.02 mg/100 ml GF; P less than 0.01), serum PTH (from 39 +/- 19 to 21 +/- 1 microliters eq/ml; P less than 0.05), and urinary cAMP excretion (from 5.30 +/- 0.57 to 3.57 +/- 0.59 nmol/100 ml GF; P less than 0.0025). The results suggested that hyperparathyroidism was secondary. Histomorphometric analysis of bone showed reduced trabecular bone volume without mineralization defect, compatible with osteoporosis. Four of eight patients had high or high normal fractional resorption surfaces, fractional formation surfaces, and fractional osteoid volumes. That these abnormalities may reflect PTH-dependent osteoclastic resorption and bone turnover was supported by the reduction of these indices after correction of secondary hyperparathyroidism with hydrochlorothiazide therapy. The remaining four patients, however, had normal histomorphometric results. In summary, postmenopausal osteoporosis may occur sometimes with renal hypercalciuria and secondary hyperparathyroidism. The lack of compensatory intestinal hyperabsorption of Ca predisposes to negative Ca balance, and the hyperparathyroid state may be manifested by stimulated osteoclastic and osteoblastic activities.

Calcium bioavailability from calcium carbonate and calcium citrate.

Fourteen normal subjects took 1000 mg calcium orally as calcium citrate or calcium carbonate. The amount of calcium absorbed was estimated from the rise in urinary calcium. The urinary calcium following calcium citrate load significantly higher (by 20-66%), whether expressed as the total amount or as the increment above basal (fasting) excretion. Thus, calcium citrate provides a more optimum calcium bioavailability than calcium carbonate.