Parathyroid hormone and parathyroid hormone-related peptide stimulate insulin-like growth factor-binding protein secretion by rat osteoblast-like cells through a adenosine 3',5'-monophosphate-dependent mechanism.

Specific insulin-like growth factor-binding proteins (IGFBPs) that may enhance or inhibit insulin-like growth factor (IGF) action are produced in various tissues. In the present study we demonstrated that IGFBPs are synthesized and secreted by rat osteoblast-like cells (UMR 106-01). PTH and PTH-related peptide (PTHrP) were potent stimuli for IGFBP production by UMR cells, whereas GH, IGF-I, insulin, epidermal growth factor, and T3 had little or no effect. A maximal 8- to 30-fold increase in IGFBP production was attained at 10(-7)-10(-6) M PTH and PTHrP, with a half-maximal effect at approximately 10(-9) M. By Western blot analysis, PTH and PTHrP markedly and selectively increased the production of 29,000 mol wt (Mr) and, to a lesser extent, 24,000 Mr IGFBPs. Agents that elevate intracellular cAMP by different mechanisms [(Bu)2cAMP, forskolin, and isobutylmethylxanthine] mimicked the effect of PTH and PTHrP on IGFBP synthesis. In comparison, PTH did not stimulate IGFBP production in fibroblasts and ROS 17/2.8 cells, which secrete IGFBPs of 42,000, 38,000, 34,000, 28,000, and 24,000 Mr, but not of 29,000 Mr. The PTH-responsive IGFBPs from UMR cells were nonglycosylated proteins with preferential affinity for IGF-I over IGF-II. These IGFBPs were not immunoprecipitated with antisera against rat IGFBP-2 or human IGFBP-1. Thus, PTH and PTHrP increase the production in UMR 106-01 cells of discrete IGFBP forms with Mr of 29,000 and 24,000 through a cAMP-mediated mechanism, independent of IGF-I synthesis. Taken with the known effects of PTH on IGF production in bone cells, the data suggest that PTH and PTHrP may modulate local IGF action in bone through the regulation of specific IGFBP availability.

Desensitization of rat osteoblast-like cells (ROS 17/2.8) to parathyroid hormone uncouples the adenosine 3',5'-monophosphate and cytosolic ionized calcium response limbs.

We have investigated the effects of PTH-induced desensitization on second messenger interactions in the rat osteosarcoma cell line ROS 17/2.8. Adenylate cyclase activation was assessed by accumulation of immunoassayable cAMP, and cytosolic calcium ion ([Ca2+]i) concentrations were measured in adherent perifused cells loaded with the Ca2(+)-sensitive bioluminescent protein aequorin. Preexposure to rat PTH-(1-34) [rPTH-(1-34); 10(-8) M for 48 h, then 10(-7) M for 24 h] dramatically reduced (by 85%) the cAMP response to fresh challenge [2 min; 10(-9)-10(-7) M rPTH-(1-34)], but the peak PTH-induced rise of [Ca2+]i was not diminished significantly (0-20%). Nevertheless, we did observe other changes in the PTH-induced [Ca2+]i response. Exposure of treated cells to (Bu)2cAMP nearly abolished the [Ca2+]i response to PTH (greater than 80% reduction), but had much less effect on the PTH-stimulated [Ca2+]i increment of the naive cells (less than 35% reduction). Treated cells also had a blunted [Ca2+]i response to PTH in the presence of low extracellular calcium (greater than 60% reduction), but in the naive cells, low extracellular Ca2+ did not significantly diminish the peak PTH-induced [Ca2+]i rise, although low extracellular Ca2+ dramatically reduced the area under this [Ca2+]i transient (greater than 50%). Low extracellular Ca2+ had no influence on the peak [Ca2+]i responses of treated cells to bradykinin or prostaglandin F2 alpha. Although the peak PTH-stimulated [Ca2+]i rise of treated cells in normal Ca2+ medium was not significantly attenuated, the time to half-maximum [Ca2+]i concentration was significantly increased (greater than 100%), and the area under the [Ca2+]i transient was diminished. These alterations in the [Ca2+]i response of treated cells were not observed upon challenge with bradykinin or prostaglandin F2 alpha. Thus, 1) the cAMP and [Ca2+]i responses of ROS 17/2.8 cells to rPTH-(1-34) are not obligatorily coupled; 2) the response of naive cells to PTH includes both the release of Ca2+ from intracellular stores and the entry of extracellular Ca2+; and 3) pretreatment of these cells with rPTH-(1-34) augments the dependence on Ca2+ entry during hormone rechallenge. We propose that the preserved PTH-stimulated [Ca2+]i rise in treated cells results partly from loss of cAMP-mediated inhibition of extracellular Ca2+ entry.

Inhibition by human interleukin-1 alpha of parathyroid hormone-related peptide effects on renal calcium and phosphorus metabolism in the rat.

Humoral hypercalcemia of malignancy (HHM) is at least partly caused by tumor secretion of PTH-related peptide (PTHrP), but there is growing evidence for cosecretion with PTHrP of other bone-resorbing peptides, such as the cytokine interleukin-1 alpha (IL-1 alpha). Administration of PTHrP in vivo and in vitro generally mimics the actions of PTH itself, with increases in both resorption and formation of bone. However, bone in HHM is characterized by uncoupling of bone turnover, with increased resorption and decreased formation. We performed experiments to determine whether IL-1 alpha might alter the effects of PTHrP and produce uncoupling. Thus, we administered to 100-g male rats by sc osmotic minipumps synthetic PTHrP-(1-34) alone (2 micrograms/100 g/day), recombinant IL-1 alpha alone (1.5 micrograms/100 g/day), both peptides together at the previous doses, or vehicle only. We infused 5 groups of 12 rats each (PTHrP, IL-1 alpha, PTHrP plus IL-1 alpha, ad libitum fed control, and controls pair-fed to the PTHrP plus IL-1 alpha group) for 14 days. At the end of the study, blood and urine were taken for chemical measurements, and tibias and femurs were harvested for histomorphometry and extraction of RNA from periosteal cells. As expected, PTHrP induced hypercalcemia, relative hypophosphatemia, phosphaturia, and reduced bone mass. Osteoblast number was increased, but osteoclast number was not. Indices of bone formation were unchanged or reduced. The dose of IL-1 alpha chosen had no statistically significant effect, except for reduced longitudinal bone growth, but when combined with PTHrP, IL-1 alpha reduced hypercalcemia, hypophosphatemia, and phosphaturia. In contrast to the blood and urine effects, IL-1 alpha did not interact significantly with PTHrP's effect on bone measurements. Northern analysis of periosteal cell mRNA showed that PTHrP reduced expression of osteocalcin, but not glyceraldehyde-3-phosphate dehydrogenase; IL-1 alpha had no additional effect. These data suggest that 1) continuously administered PTHrP alone may induce uncoupled bone turnover with decreased cortical bone formation; 2) IL-1 alpha appears to inhibit strongly the renal effects of PTHrP and weakly (if at all) its actions on bone and, thus, to decrease its hypercalcemic, phosphaturic, and hypophosphatemic actions; and 3) cosecretion of IL-1 alpha, and possibly other peptide cytokines, with PTHrP may modify the clinical expression of HHM.

Plasma intact parathyroid hormone (PTH) and PTH-related peptide in familial benign hypercalcemia: greater responsiveness to endogenous PTH than in primary hyperparathyroidism.

The cause of hypercalcemia in familial benign hypercalcemia (FBH; also called familial hypocalciuric hypercalcemia) is unclear, although it is PTH dependent. It is also uncertain how plasma PTH levels are related to the severity of biochemical abnormalities in FBH. Because the PTH-related peptide (PTHrP) has many PTH-like actions, it might have a role in the hypercalcemia of FBH. Thus, we studied 29 patients with FBH from 11 families, 29 age- and sex-matched controls, and 42 patients with primary hyperparathyroidism (1 degree HPT), measuring PTH with a highly sensitive two-site immunochemiluminometric assay and the hypercalcemic tumor factor PTH-related peptide (PTHrP) with an extraction/concentration RIA. Plasma PTH values were elevated in 86% of 1 degree HPT patients (36 of 42), but in only 20% of FBH patients, (6 of 29). Plasma PTHrP was elevated in 1 FBH patient, and the group mean value was normal. Plasma PTH was positively correlated with calcium (Ca) in 1 degree HPT (r = 0.66; P less than 0.0001) and in FBH (r = 0.53; P less than 0.004), but the slopes of the regressions were markedly different: 1 degree HPT, 6.72; FBH, 1.61 (P less than 0.0001). There was a negative correlation between PTH and phosphorus (P) in 1 degree HPT (r = -0.39; P less than 0.01) and in FBH (r = -0.41; P less than 0.03), but, again, the slopes differed greatly: 1 degree HPT, -6.57; FBH, -1.95 (P less than 0.0001). There were no correlations between PTHrP and Ca or between PTH and PTHrP. The sums and products of PTH and PTHrP were not better correlated with Ca than PTH alone. Thus, PTH values are lower at given Ca and P levels in patients with FBH than in those with 1 degree HPT, suggesting that PTH is more effective in raising Ca and lowering P in FBH than in 1 degree HPT. The enigma of FBH remains: what molecular defect can simultaneously cause parathyroid cell insensitivity to Ca, enhanced renal tubular reabsorption of Ca, increased renal rejection of P, and enhanced or retained sensitivity to PTH?

Cyclic adenosine 3',5'-monophosphate responses to parathyroid hormone, prostaglandin E2, and isoproterenol in dermal fibroblasts from patients with familial benign hypercalcemia.

Plasma concentrations of PTH are much lower for a given calcium or phosphorus level in patients with familial benign hypercalcemia (FBH, or familial hypocalciuric hypercalcemia) than in those with primary hyperparathyroidism; these and other data suggest that there might be tissue hypersensitivity to PTH in FBH. To test this hypothesis, we have used cultured dermal fibroblasts from abdominal skin biopsies of six patients with FBH and six age- and sex-matched controls as surrogate PTH-responsive tissues. Cells in 24-well plastic plates were exposed to vehicle, human PTH-(1-34) (10(-10)-10(-7) M), prostaglandin E2 (10(-6) M), or isoproterenol (10(-4) M) for 10 min in the presence of isobutylmethylxanthine, and cellular cAMP was determined by RIA. All cells responded to PTH with dose-dependent increases in cAMP, and all responded strongly to prostaglandin E2 and isoproterenol. There were no consistent or significant differences between control and FBH fibroblasts in maximal responses to the three agonists, and half-maximal stimulation was achieved with about 10(-9) M PTH in both normal and FBH cells. These data are not consistent with increased tissue sensitivity to PTH in FBH.

Calcium infusion suggests a "set-point" abnormality of parathyroid gland function in familial benign hypercalcemia and more complex disturbances in primary hyperparathyroidism.

PTH clearly plays a role in maintaining the hypercalcemia of familial benign hypercalcemia (FBH or familial hypocalciuric hypocalcemia). To better define the abnormalities of parathyroid function in FBH and primary hyperparathyroidism (1 degree HPT), we used a two-site immunochemiluminometric assay for intact PTH to examine PTH suppressibility in normal individuals and patients having FBH or 1 degree HPT. Twelve normal, 11 FBH, and 7 1 degree HPT subjects were given calcium (Ca) iv with frequent sampling for ionized Ca and intact PTH. In normal and FBH subjects, plasma PTH levels decreased essentially identically in response to iv Ca. In the 1 degree HPT group, PTH was not normally suppressible. However, there was a spectrum of responsiveness in 1 degree HPT patients, with a significant correlation between tumor mass and degree of PTH nonsuppressibility (r = 0.87, P = 0.01). Analysis of the relationship between plasma PTH and ionized Ca values in the three groups demonstrated a shift to the right in the FBH curve, with no difference of slope, consistent with the notion of a simple "set-point" error in FBH. In contrast, the curve in 1 degree HPT was not only shifted to the right but also differed from normal in slope (normal, -8.92; 1 degree HPT, -3.92, P = 0.04). Thus, we propose that the parathyroid functional abnormality in FBH represents a simple set-point error, whereas the defect in 1 degree HPT consists of a set-point error combined with varying degrees of Ca nonsuppressible PTH secretion that may be related to tumor mass.

[Protein metabolism in women receiving Stediril-Wyeth preparation as a contraceptive]. / Gospodarka bialkowa u kobiet przyjmujacych preparat Stediril-Wyeth w celach antykoncepcyjnych

PIP: 33 women, aged 20-41 years, used the contraceptive preparation Stediril, produced by the firm Wyeth, over the course of 6 menstrual cycles. 20 healthy women of the same age groups were used as a control. The total serum proteins and serum protein fractions were determined in both groups. It was determined in the group using the preparation, that after 6 weeks of use the serum protein pattern was altered. This alteration was through a decrease in the content of the globulin beta and gamma fractions. Results from the statistical analysis of the mean arithmetic values of the serum albumins is presented.^ieng

[Effect of the oral contraceptive preparation Femigen on the erythrocyte and resin uptake of 131-I-triiodothyronine]. / Wplyw preparatu femigen stosowanego dla celów antykoncepcyjnych na wartosci wychwyu erytrocytowego i zywicowego 131-J-trójjodotyroniny.

PIP: 150 women, 50 in the 1st and 3rd trimesters of normal pregnancy, 50 in the 6th month of curation administered by Femigen-forte, and the same 50 women 3 months after discontinuation of the use of the preparation, were given erythrocyte and resin up-take tests for labeled triiodothyronine. The values obtained from the women who had used the Femigen preparation were similar to the values obtained from those women in normal gestation. The results of the group of women who had discontinued the use of Femigen normalized, although there were some age-linked differences within this group; results in women aged 31-42 years were slightly lower than in those women aged 20-30 years.^ieng

Comparison of body composition by bioelectrical impedance analysis and dual-energy X-ray absorptiometry in Hispanic diabetics.

OBJECTIVE: The purpose of this study was to compare Tanita tetrapolar foot-to-foot bioelectrical impedance analysis (Model TBF-310, Tanita Corporation of America, Inc, Arlington Heights, IL; Tanita-BIA) and fan beam dual-energy X-ray absorptiometry (Hologic Discovery A v12.6, Waltham, MA; DXA) in diabetic patients. METHODS: Seventy Hispanic diabetic participants (23 male, 47 female; mean age: 53.03 ± 10.32 yrs; mean weight: 81.45 ± 17.65 kg; and mean body mass index: 31.40 ± 6.80 kg/m(2)) were selected from the Loma Linda University En Balance culturally-sensitive Spanish diabetes education program using the baseline data. RESULTS: DXA vs Tanita-BIA fat mass (FM), percent fat mass (%FM), and fat-free mass (FFM) were compared using Pearson's (FM: 0.96, %FM: 0.91, and FFM: 0.95), and Spearman's rank (FM: 0.94, %FM: 0.91, and FFM: 0.93) correlation coefficients. Bland-Altman analyses were also used to compare the difference (DXA - BIA) vs average of DXA and BIA results and showed general agreement between the two methods. When Tanita-BIA was regressed onto DXA, the adjusted R(2) was: FM=0.91; %FM=0.83; FFM=0.90. Gender combined concordance correlations with 95% confidence intervals were calculated using a bootstrap re-sampling of the data and found high associations [FM: 0.93 (95% CI: 0.89, 0.96)], [%FM: 0.86 (95% CI: 0.79, 0.90)], and [FFM: 0.93 (95% CI: 0.89, 0.96)]. CONCLUSION: Tanita-BIA may provide valid measures of fat, percent body fat and fat-free mass in Hispanic diabetics, and could be a convenient and practical approach for assessment in community-based research.

Effect of the EnBalance, a culturally and language-sensitive diabetes education program, on dietary changes and plasma lipid profile in Hispanic diabetics.

OBJECTIVE: To assess the effects of a language-sensitive diabetes education program on dietary changes and plasma lipid profiles. METHOD: Hispanic participants (n=13 males and 18 females, mean age = 54.00 + 10.68 years) participated in a 3-month health education study. Spearman correlation coefficients were used to evaluate correlations between dietary intake and laboratory measurements. RESULTS: There were significant decreases in serum total cholesterol (-16.07 mg/dl, P= 0.035), HDL cholesterol (-3.23 mg/dl, P = 0.01), LDL cholesterol (-11.71 mg/dl, P = 0.013) and dietary cholesterol (-79.22 mg, P = 0.03). No significant mean change was observed in triglyceride and total cholesterol/HDL ratio. There was also a reduction in body mass index (BMI) (-0.15 kg/m(2), P = 0.40), fasting glucose (-3.90 mg/dl, P = 0.43) and dual energy X-ray absorptiometry (DXA) total fat (-0.50, P = 0.97). Although not statistically significant, saturated fatty acids (-4.90 g, P = 0.19), polyunsaturated fatty acids (-3.31g, P = 0.11), and carbohydrate (-44.82 g, P = 0.22), decreased after three months. CONCLUSION: There were significant improvements in dietary intake and serum lipids after a three-month culture-specific diabetes education program.

Magnesium and zinc deficiency and growth retardation in offspring of alcoholic rats.

Alcohol ingestion during pregnancy is known to cause fetal malformation and growth retardation. We investigated the effect of alcohol on mineral content and fetal development in rats fed 24% (v/v) alcohol eight weeks prior to and during pregnancy. Rats ingesting alcohol produced fewer fetuses (6.3 +/- 0.3 vs 9.6 +/- 0.3 in control) with lower fetal weight (3.48 +/- 0.09 vs 4.12 +/- 0.08 gm in control) and heavier placentas (0.66 +/- 0.05 vs 0.50 +/- 0.01 gm in control). The fetuses of alcoholic rats contained lower zinc (423.8 +/- 4.5 vs 459.9 +/- 5.4 microEq/100 gm dry weight in control) and magnesium (12.4 +/- 0.1 vs 12.7 +/- 0.1 mEq/100 gm dry weight in control) in the total carcass.

The effect of hypomagnesemia with or without associated hypercalcemia on renal concentrating ability in rats.

The effect of hypomagnesemia on renal concentrating ability was assessed in rats fed diets either low in magnesium or low in magnesium and calcium for 30 days. The rats fed a low-magnesium diet became hypomagnesemic (0.26 +/- 0.03 versus 1.53 +/- 0.04 mEq/L in controls), hypercalcemic (5.96 +/- 0.04 versus 5.22 +/- 0.11 mEq/L in controls), and hypokalemic (3.1 +/- 0.1 versus 4.2 +/- 0.4 mEq/L in controls) with decreased muscle content of potassium. Despite being hypomagnesemic, hypercalcemic, and potassium depleted, the rats had normal renal concentration ability (2499 +/- 65 versus 2415 +/- 119 mOsm/kg H2O in control). Those rats fed a diet low in both magnesium and calcium became hypomagnesemic (0.41 +/- 0.08 versus 1.53 +/- 0.04 mEq/L in controls) but were hypocalcemic. They also had normal renal concentrating ability (2399 +/- 109 versus 2415 +/- 119 mOsm/kg H2O in controls). It is concluded that hypomagnesemia does not decrease renal concentrating ability in rats. Furthermore, a normal concentrating ability demonstrated in hypomagnesemic rats, in spite of hypercalcemia and potassium depletion suggests that hypomagnesemia may ameliorate the deleterious effects of hypercalcemia and/or potassium depletion on renal concentrating ability.

Source of urinary cyclic AMP in response to calcitonin and parathyroid hormone in the rat.

Administration of calcitonin (CT) or parathyroid hormone (PTH) in rats, induced phosphaturia with a concomitant increase in urinary excretion of cyclic AMP. CT produced a rise in arterial cAMP and filtered cAMP, with no increase in urinary nephrogenous cAMP. PTH on the other hand, produced an elevation in urinary nephrogenous cAMP with no increase in arterial cAMP and filtered cAMP. These results indicate that the source of urinary cAMP after CT is non-renal, whereas after PTH it is renal in origin.