Bone Hydroxyproline Research Articles

Growth Rate and Bone Hydroxyproline Concentration in Turkeys Fed with a Silage-Composed Diet Modified with Different Diet Cation-Anion Differences (DCADs).

Simple SummaryIn this study, we point to the possibility of using dietary cation–anion difference manipulation to improve growth rates and bone condition, especially in the last phase of poultry turkey husbandry, when birds have many bone abnormalities. Our goal was to determine the responses of body weight (BW) and bone hydroxyproline (Hyp) concentration in turkeys fed a corn silage (CS) diet with different values of dietary cation–anion differences (DCADs). The turkeys (n = 90) were divided into five groups and fed as follows: group A (control)—standard diet (SD) (60%) plus CS (40%); group B—SD (60%), CS (40%) plus 240 g of CaCl2 per 100 kg of diet; group C—SD (60%), CS (40%) plus 480 g of CaCl2 per 100 kg of diet; group D—SD (60%), CS (40%) plus 240 g of NaHCO3 per 100 kg of diet; group E—SD (60%), CS (40%) plus 480 g NaHCO3 per 100 kg of diet. The addition of a lesser amount of CaCl2 lowered the DCAD, which ranged between 52.5 ± 4.19 and 91.14 ± 3.14 mEq/kg DM. An increased content of CaCl2 led to high negative values of DCAD. NaHCO3 supplemented in both doses resulted in a significant elevation of DCAD. Compared to each experimental group, feeding birds with a diet supplemented only with CS resulted in a lower BW. Addition of CaCl2 or NaHCO3 to the diet improved BW, but only CaCl2 addition enhanced the bone Hyp amount. In conclusion, we suggest that an anionic diet with low DCAD can prevent bone abnormalities in large turkeys, especially in the final course of production.

Effect of Collagen Hydrolysates from Silver Carp Skin (Hypophthalmichthys molitrix) on Osteoporosis in Chronologically Aged Mice: Increasing Bone Remodeling

Osteoporosis is a common skeletal disorder in humans and gelatin hydrolysates from mammals have been reported to improve osteoporosis. In this study, 13-month-old mice were used to evaluate the effects of collagen hydrolysates (CHs) from silver carp skin on osteoporosis. No significant differences were observed in mice body weight, spleen or thymus indices after daily intake of antioxidant collagen hydrolysates (ACH; 200 mg/kg body weight (bw) (LACH), 400 mg/kg bw (MACH), 800 mg/kg bw (HACH)), collagenase hydrolyzed collagen hydrolysates (CCH) or proline (400 mg/kg body weight) for eight weeks, respectively. ACH tended to improve bone mineral density, increase bone hydroxyproline content, enhance alkaline phosphatase (ALP) level and reduce tartrate-resistant acid phosphatase 5b (TRAP-5b) activity in serum, with significant differences observed between the MACH and model groups (p < 0.05). ACH exerted a better effect on osteoporosis than CCH at the identical dose, whereas proline had no significant effect on repairing osteoporosis compared to the model group. Western blotting results demonstrated that CHs mainly increased bone remodeling by stimulating the transforming growth factor β1 (TGF-β1)/Smad signaling pathway and improving the interaction between collagen and α2β1 integrin. The results indicated that CHs from fish could be applied to alleviate osteoporosis or treat bone loss.

The effect of human-like collagen calcium complex on osteoporosis mice

The objective of this study was to assess the effect of a modified human-like collagen calcium complex on osteoporosis mice. BHK (Baby Hamster Kidney) cells were used to compare the cytotoxicity of different calcium reagents with the MTT test. Six-week-old male mice (n = 80) were randomly divided into eight groups: a blank group (blank), control group (control), human-like collagen calcium group (HLC-Ca), thiolated human-like collagen calcium group (SH-HLC-Ca), phosphorylated human-like collagen calcium group (Pi-HLC-Ca), gluconate group (Glc-Ca), calcium carbonate group (CaCO3) and D-cal group (B). A systematic analysis of the results available in vivo after 3 months of treatment was presented. The effects of several Ca supplements on osteoporosis mice were investigated by detecting serum calcium, alkaline phosphate activity (ALP), bone hydroxyproline (BHP) and bone mineral density (BMD). The results proved that the BMD and BHP of osteoporosis mice were significantly increased in the Pi-HLC-Ca group, while serum calcium and ALP were decreased. Therefore, Pi-HLC-Ca is likely a good calcium supplement for clinical applications. In this review, the advantage of Pi-HLC-Ca in preventing and delaying osteoporosis is highlighted. In addition to the current progress, further investigations are necessary to reveal the relative influences of collagen and calcium proportions on the long-term clinical effects of osteoporosis.

Impacts of Ultra-early Hyperbaric Oxygen Therapy on Bone Mass of Rats With Complete Spinal Cord Transection.

Seventy-five SD rats were randomly assigned to four groups: sham-operated group (Sham, n = 15), complete spinal cord transection (CSCT, n = 20) group, hyperbaric oxygenation group 1 (HBO1, n = 20), and hyperbaric oxygenation group 2 (HBO2, n = 20). The aim of this study was to analyze the impacts of ultra-early hyperbaric oxygen therapy on bone mass of rats with CSCT. Treatment of patients with complete SCI is still an unresolved medical issue and needs to be further investigated. Studies on changes in bone mass as well as osteoporosis prevention after SCI have important clinical significance. Rats in the sham group only underwent T10 laminectomy, without damaging the spinal cord. Rats in CSCT, HBO1, and HBO2 groups underwent T10 laminectomy and spinal cord transection at T10 level. Rats in HBO1 and HBO2 groups received three courses of hyperbaric oxygen therapy with 10 days per course starting at 3 and 12 hours after spinal cord injury, respectively. The femoral biomechanical characteristics, the bone calcium, and the bone hydroxyproline (B-HYP) contents were determined. Morphology of the femur bone trabecula and the bone collagen were observed by HE staining and by masson triad color staining, respectively. After 6 weeks of treatment, rats in the CSCT group showed significant decreases in femur structural and material mechanics parameters, calcium and B-HYP contents, (P < 0.01), as well as sparse, fractured, malaligned trabecular bone and collagen compared with rats in the sham group. After treatments, compared with rats in the CSCT and HBO2 groups, rats in HBO1 group showed enhancement in femur structural and material mechanics parameters, calcium and B-HYP contents, (P < 0.05), as well as trabecular bone and collagen with better continuity and neater arrangement. Ultra-early HBO therapy can significantly improve bone mass in CSCT rats. N/A.

Calcium Requirements of Growing Rats Based on Bone Mass, Structure, or Biomechanical Strength Are Similar

Although calcium (Ca) supplementation increases bone density, the increase is small and the effect on bone strength and fracture risk is uncertain. To investigate if bone mass, morphology, and biomechanical properties are affected by deficient to copious dietary Ca concentrations, the long bones (tibia and femur) of growing female Sprague-Dawley rats (8/group) were assessed after 13 wk of consuming 1, 2, 3, 4, 5, 6, or 7 g Ca/kg of a modified AIN-93G diet. Dietary phosphorous (P) and vitamin D remained constant at recommended concentrations. The assessment included mineralization, density, biomechanical properties of breaking by a 3-point flexure test, and morphological properties by microcomputed topography scanning of trabecular bone of the proximal tibia metaphysis. Dietary treatment did not affect food intake, weight gain, renal and muscle Ca concentrations, and bone hydroxyproline. All bone parameters measured were significantly impaired by Ca deficiency in rats fed the diet containing 1 g Ca/kg. Modest impairments occurred with some parameters (bone density, biomechanical bending moment, modulus of elasticity, and stress) in rats fed 2 g Ca/kg, but all parameters stabilized between 2 and 3 g/kg diet, with no differences between 3 and 7 g/kg. The results suggest that a threshold response in bone Ca retention or bone mass at ∼2.5 g Ca/kg diet is associated with similar threshold responses in bone breaking strength and related biomechanics as well as trabecular structural properties. There was no evidence of a relative P deficiency or of improved or impaired bone strength and structure as Ca intakes increased beyond those needed to maximize bone density.

Intrauterine transplantation of human fetal mesenchymal stem cells from first-trimester blood repairs bone and reduces fractures in osteogenesis imperfecta mice

AbstractThe inherited skeletal dysplasia osteogenesis imperfecta (OI) results in multiple fractures and is currently treated empirically. We transplanted human first-trimester fetal blood mesenchymal stem cells (MSCs) into homozygous oim mice in utero. This resulted in a two-thirds reduction in long bone fractures (P < .01), with fewer fractures per mouse (median 1, range 0-2 in mice that received transplants vs median 3, range 1-5 in mice that did not receive transplants by 12 weeks, P < .01). Nearly all mice that did not receive transplants had fractures (47 [97.9%] of 48), in contrast to 17 (58.6%) of 29 4- to 12-week-old mice that received transplants (P < .01). Transplantation was associated with increased bone strength (P < .01), thickness (P < .01), and length (P < .01), and normalization/reduction of growth plate height in 4- to 12-week-old oim was reduced in mice that underwent transplantion (P < .001). More donor cells were found in bone tissues compared with other organs (P < .001), with cells clustered in areas of active bone formation and remodeling, and at sites of fracture healing. Donor cells found in the bone expressed osteoblast lineage genes, and produced the extracellular bone structural protein osteopontin. Finally, MSC transplantation decreased bone hydroxyproline content. In conclusion, intrauterine transplantation of fetal MSCs markedly reduced fracture rates and skeletal abnormalities in a mouse model of the intermediate severity type III OI, suggesting a scientific basis for MSC treatment of affected human fetuses.

Quantitation of hydroxyproline in bone by gas chromatography–mass spectrometry

A validated gas chromatography (GC)–mass spectrometric (MS) method for the analysis of hydroxyproline in rat femur is reported. Hydroxyproline in bone hydrolysates was extracted with an anion exchange resin and the N(O)- tert-butyldimethylsilyl derivatives analyzed by GC–MS. The hydroxyproline concentration was estimated relative to pipecolic acid, 3,4-dehydroproline and n-tetracosane as internal standards. The mass-to-charge ratios ( m/ z) for the ions used for quantitation by single ion monitoring were 314 m/ z for hydroxyproline, 198 m/ z for pipecolic acid, 256 m/ z for dehydroproline and 57 m/ z for n-tetracosane. A coefficient of variation of 5.8% was achieved and the limit of detection was calculated to be 0.233 μmol/l bone hydrolysate.

Metabolic studies on connective tissue collagens in bone and tendon of adjuvant arthritic rat.

The metabolic alterations in the matrix of connective tissue collagen were investigated in bone and tendon of rats with adjuvant-induced arthritis. Adjuvant arthritis was induced in rats with the immunization of Freund's adjuvant containing heat-killed Mycobacterium tuberculosis. The changes in the metabolism of collagen were studied using radioactive isotopic measurements with (3H)-proline. Tissue specimens were fractionated individually into soluble and insoluble collagens. The synthesis of collagen was examined by measuring the total collagen content and the radioactivity of (3H)-hydroxyproline in soluble collagen fraction within 24 hours after the administration of tritiated proline. The conversion of soluble to insoluble collagen was analyzed by measuring the radioactivity of (3H)-hydroxyproline in both soluble and insoluble collagens. The catabolism of soluble and insoluble collagens was studied by estimating the radioactivity of urinary (3H)-hydroxyproline 24 hours after the injection of tritiated proline. It was observed that the total collagen content and the total radioactivity of (3H)-hydroxyproline in bone and tendon were decreased significantly in adjuvant arthritic rats. The specific and total radioactivities of (3H)-hydroxyproline in soluble collagen were found to be reduced, indicating the decreased de novo synthesis of collagen during the diseased state. The conversion of soluble to insoluble collagen was impaired in tissues as evidenced by the increased content of soluble collagen in arthritic disease. In addition, an enhanced excretion of hydroxyproline was found in urine of arthritic rats, indicating the increased degradation of collagen in arthritic disease. These observations could, therefore, explain in part the changes in synthesis and degradation of collagen in bone and tendon during the development of experimentally induced adjuvant arthritis in rats.

Modulation of ovariectomy-related bone loss by parathyroid hormone in rats

Studies were carried out to examine whether parathyroid hormone (PTH) will prevent the age-related bone loss that results from ovarian hormone deficiency and to explore the mechanism of its action. Ovariectomy caused a significant decrease in bone density in the distal metaphysis and mid-diaphysis, but not in the vertebra and proximal metaphysis. The decrease was prevented by PTH injection and in all the bones examined PTH administration increased bone density and bone calcium content above the levels in sham-operated controls. Similar findings were made in bone hydroxyproline levels. PTH treated ovariectomized animals had lower serum 25(OH)vitamin D and higher 1,25(OH) 2 vitamin D levels than ovariectomized and sham operated animals that received solvent vehicle. Compared to the sham operated controls, ovariectomy caused a 4.5-fold increase in the number of tartrate resistant acid phosphatase (TRAP) positive multinuclear cells. This increase did not occur in PTH-treated animals. We conclude that PTH is effective in preventing ovarian hormone deficiency bone loss in rats. PTH may mediate this effect partly by stimulating osteoblastic bone formation and partly by increasing 1,25(OH) 2 vitamin D-mediated calcium absorption. The data from TRAP positive multinuclear cells indicate that an etiologic component of ovarian hormone deficiency bone loss is the expansion of a pool of osteoclast progenitors and that the bone anabolic action of PTH involves, in part, a decrease in bone resorption as a result of the suppression of the proliferation of osteoclast progenitors.

Comparison of the effect of gluconate, lactose, and xylitol on bone recalcification in calcium-deficient rats

The therapeutic value of three calcium absorption promoting carbohydrates, lactose, gluconate and xylitol, in bone calcification was evaluated in 7-week-old male rats which were fed on a semisynthetic Ca-deficient diet for 3 weeks. Lactose + CaCO 3, xylitol + CaCO 3, Ca-gluconate, or CaCO 3 alone were administered to the Ca-deficient rats for 2 weeks; the carbohydrate and Ca contents of the diets were 5% and 0.5%, respectively. The Ca-deficient rats showed a decrease in serum total Ca and ionized Ca 2+ and in tibial Ca, Mg, P and density, with a concomitant increase in bone hydroxyproline concentration. Bone and serum tartrateresistant acid phosphatase activities were increased 2-fold and the serum 1,25(OH) 2D 3 level 5-fold. Smaller increases were found in serum calcitonin, PTH, alkaline phosphatase and osteocalcin levels. These changes (except calcitonin) were reversed by the administration of Ca and the carbohydrates. It was observed that all three agents improved the recalcification of bones compared with the effect of CaCO 3 alone. The effect of lactose and xylitol was superior to that of gluconate. These results suggest advantages in the use of xylitol in Ca-supplements.

Treatment of experimental silicosis with antifibrotic agents

We tested the efficacy of 2 antifibrotic agents, the proline analogue cis-4- hydroxy- l- proline (cHyp) and the lathyrogen β-aminopropionitrile (BAPN), on experimental silicosis in hamsters. Silica (75 mg) was instilled intratracheally, and 3 months later lung hydroxyproline content, the volume density of silicotic nodules in lung parenchyma, fluid-filled lung pressure-volume curves, body weight and survival were measured. Animals were injected with cHyp, 200 mg/kg body weight, or BAPN, 150 mg/kg body weight, twice daily for 3 months. Hydroxyproline contents (mg/lung) at 3 months were: control, 0.8 ± 0.1; silica, 1.4 ± 0.1 ( P<0.05 compared to control); silica-cHyp, 1.2 ± 0.2; silica-BAPN, 1.4 ± 0.1 (both NS compared to silica). The volume density of granuloma (% of surface area) was: silica, 0.7 ± 0.1; silica-cHyp, 5.9 ± 1.0; silica-BAPN, 9.7 ± 1.5 (both P < 0.5 compared to silica). There was no difference among the groups as assessed by lung pressure-volume curves. No toxic effects were produced on the skeletal system as assessed by bone hydroxyproline content and skeletal roentgenograms. Final body weights (g) were: silica, 114 ± 5; silica-BAPN, 108 ± 6; silica-cHyp, 88 ± 7 (the latter P<0.05 compared to silica). Survival (%) was: silica, 62%; silica-BAPN, 34%, silica-cHyp, 28% (both P<0.05 compared to silica). These data show that cHyp and BAPN treatment did not prevent silica-induced pulmonary fibrosis, led to more extensive silicotic nodules, and were toxic. Both cHyp and BAPN have some efficacy in other models of fibrosis, and the observations in the present study could be specific to silicosis in the hamster.

Inhibition of bone resorption in vitro by serine-esterase inhibitors

The effect of two synthetic serine esterase inhibitors, N- α-dansyl( p-guanidino)phenylalaninepiperidine hydrochloride (I 2581) and d-phenylalanyl- l-prolyl- l-arginine chloromethyl ketone ( d-Phe-Pro-Arg-CH 2Cl), on bone resorption in organ cultured mouse calvaria from neonatal mice has been examined. Mineral mobilization was assessed by analyzing the release of 45Ca, stable calcium (Ca 2+) and inorganic phosphate (P i). Organic matrix degradation was studied by analyzing the release of 3H from [ 3H]proline-labelled bones, and by quantifying the amounts of hydroxyproline in bone after culture. It was found that I 2581, at and above 30 μmol/l, dose-dependently inhibited 45Ca release induced by thrombin, parathyroid hormone (PTH), prostaglandin E 2 and 1-α-hydroxyvitamin D-3. I 2581 (50 μmol/l) inhibited PTH-stimulated release of 3H from [ 3H]proline-labelled bones, and this effect was reversible after withdrawal of I 2581. I 2581 (50 μmol/l) inhibited the release of Ca 2+, P i, β-glucuronidase and β- N-acetylglucosaminidase in bones stimulated by PTH and 1-α-hydroxyvitamin D-3, without affecting the release of lactate dehydrogenase. In parallel, I 2581 decreased PTH and 1-α-hydroxyvitamin D-3 induced reduction of hydroxyproline levels in bones after culture. I 2581 (50 μmol/l) did not affect the basal release of 45Ca, Ca 2+, β-glucuronidase and β- N-acetylglucosaminidase, nor the basal amounts of hydroxyproline in bones after culture. d-Phe-Pro-Arg-CH 2Cl (100 μmol/l) significantly inhibited PTH- and PGE 2-induced release of 45Ca without affecting basal release of radioactive calcium. These data indicate that activation of serine proteinase(s) may be a necessary step in the mechanism of action of several stimulators of bone resorption.

New Bone Formation and Parathyroid Activity Effected by 1 ??-Hydroxyvitamin D3

Adult male rats reared on a standard diet were treated with peroral dosages of 1 alpha-hydroxyvitamin D3 (1 alpha-OHD3). A rapid effect on the serum calcium level was found; the elevation (compared to untreated controls) occurred as early as two weeks and remained elevated throughout the treatment period. Histomorphometric analysis revealed a decreased resorption rate and increased incorporation of tetracycline after four weeks of 1 alpha-OHD3 treatment. These results were associated with a significant increase of cortical as well as trabecular bone, as well as increased levels of bone hydroxyproline and hexosamines. A clearly significant decrease in the total volume of parathyroids was found after six weeks; this was accompanied by a slight pycnosis of the chief cells, which may account for reduced parathyroid activity.

The Long Term Effect of Estrogen Administration on the Metabolism of Male Rat Bone

Hundred and fifty-gram male rats were divided into four groups with the first containing intact controls, the second intact animals treated with 400 μg per 100 g body wt of 17-β-estradiol twice a week. The animals in the third group were castrated and those in the fourth were castrated and treated with the same dosage of estrogen. Animals were sacrificed at varying periods of time from one to 12 months. Estrogen administration caused a sustained decrease in body weight in the intact animal but did not change the body weight in castrated animals. Estrogen had no effect on either serum calcium or serum phosphorus. Estrogen administration to the intact animal caused a small but significant increase in ash content of bone. Castration caused a small decrease in this value which was still present at 12 months and estrogen administration returned the value to normal. Estrogen administration caused a decrease in total hydroxyproline content of bones of intact animals. Castration did not alter this value but estrogen administration to the castrated animal decreased the bone hydroxyproline content. Hydroxyproline incorporation rates were decreased in bones of both the intact and castrated animals. Castration did not alter the total hexosamine content of bones but estrogen administration to both the intact and castrated animals caused an increase in bone hexosamine content. Estrogen administration caused a decrease in the synthesis rate of proteoglycans in bones of both the intact and castrated animals. Estrogen administration caused a decrease in the uptake of radioactive calcium into bones of both the intact and castrated animals. There was no significant effect of estrogen on collagenolytic activity in male rat bone. It is concluded that estrogen administration to the male rat, causes changes which are different from those found in the female. There appeared to be no change in serum calcium or phosphorus values. A decreased synthesis of bone matrix and decreased uptake of radioactive calcium brought about no measurable change in the resorption of bone matrix.

Comparison of effects of parathyroidectomy and ethane-1-hydroxy-1,1-diphosphonate (EHDP) administration upon bone synthesis of hydroxyproline and urinary excretion of hydroxyproline in rats

Disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) may impair mineralization and reduce turnover of bone. However, its administration has been shown to lead to an accumulation of osteoid in both man and the rat. Using rats, the effects of surgical parathyroidectomy and administration of EHDP (30 mg EHDP/kg body weight by subcutaneous injection daily for 5 days) upon bone composition, uptake of3H-proline into hydroxyproline in bone and the subsequent urinary excretion of labelled and unlabelled hydroxyproline have been compared. Both parathyroidectomized (PTX) rats and EHDP-treated animals accumulated more hydroxyproline in bone and excreted less total urinary hydroxyproline than sham-PTX control animals, the changes induced by EHDP being of greater magnitude than those induced by surgical parathyroidectomy. Skeletal buildup of hydroxyproline was associated with decreased catabolism of mature collagen rather than enhanced synthesis of hydroxyproline in bone. EHDP administration, although decreasing urinary excretion of newly synthesised hydroxyproline, did not alter the skeletal synthesis of hydroxyproline as measured by uptake of3H-proline. In all parameters measured, responses to EHDP were similar in PTX and sham-PTX rats. It is concluded that depression of parathyroid hormone mediated bone turnover may have contributed to, but did not fully account for, the lowering of bone turnover and changes in bone composition induced by EHDP in sham-PTX rats in the present experiment.

The effect of different doses of oestradiol-17 beta on collagen synthesis in the femur of castrated female rats.

The effect of different doses of oestradiol-17beta on collagen metabolism in the femur of castrated young mature female rats was studied. The animals received daily injections of the hormone for 21 days and 25 muCi [14C] proline was injected intraperitoneally 24 h before the rats were sacrificed. The rats receiving 1 mug oestradiol per day had a significantly higher specific activity of hydroxyproline in bone compared to the normal and the castrated control rats. At the same time the bone weights and collagen content per femur was less in the rats receiving oestradiol 1 and 2 mug/day than in the control animals. The higher specific activity of bone hydroxyproline in the rats receiving oestradiol-17beta 1 mug/day did not, however, indicate a higher bone collagen accretion rate. As all rats received the same amount of [14C] proline, and the body weights differed considerably at sacrifice, tha naimals probably had different tissue fluid concentrations of [14C] proline. This possibility was supported by the observation that serum concentrations of radioactivity were inversely correlated to body weights. "Correcting" for differences in body weights, the castrated control rats turned out to be the group with the highest specific activity. On doses of 10 and 20 mug oestradiol-17beta per day, the specific activity of hydroxyproline in bone was lower than in the control rats while bone weights and collagen content of the femur were not different from the corresponding values of the castrated controls. This finding suggests a "slow down" of collagen metabolism - both with regard to the accretion and the resorption.

Effect of glucagon on bone collagen metabolism in the rat.

SUMMARY The effect of glucagon on bone was studied in rats. Urinary hydroxyproline excretion and incorporation of [3H]proline into bone hydroxyproline were used as indices of bone collagen breakdown and formation respectively. Parathyroid extract (15 USP units/rat/h, i.v.), infused into thyroparathyroidectomized animals, increased urinary hydroxyproline excretion. This increase was nullified by simultaneous administration of glucagon (50 μg/rat/h, i.v.). Rats treated with glucagon for 12 days (30 μg/100 g/day, s.c.) excreted slightly less hydroxyproline in their urine than controls. In both intact and thyroparathyroidectomized rats, glucagon (10 μg/100 g/h, s.c.) decreased incorporation of [3H]proline into bone. Similar results were obtained in nephrectomized rats, evidence that changes produced by glucagon were not solely due to alterations in proline pool size caused by increased renal excretion. From these data it is concluded that: (1) glucagon can inhibit bone resorption (the effect being slight in normal rats, but easily demonstrable in parathyroid hormone-treated thyroparathyroidectomized rats), (2) release of endogenous calcitonin is not required to produce this effect, (3) parathyroid hormone and glucagon may act on the same target cell in bone, (4) inhibition of skeletal resorption may contribute to glucagon-induced hypocalcaemia, and (5) the hormone possibly decreases bone formation. Since pharmacological doses of glucagon were used in our studies, the relationship of the observations made to the physiological role of glucagon is unknown.

Effect of calcitonin on (3H)proline incorporation into bone hydroxyproline in the rat.

SUMMARY The effect of calcitonin on the incorporation of [3H]proline into bone hydroxyproline was investigated in young growing rats. The action of the hormone was studied under the following conditions: (1) acutely, in both intact and thyroparathyroidectomized rats, (2) after 20 days of daily treatment in both intact and thyroparathyroidectomized animals, (3) in thyroparathyroidectomized animals treated with parathyroid extract for 20 days, and (4) in animals fed a low calcium diet for 25 days. Calcitonin had no effect when given either acutely or long-term to intact animals. [3H]Proline incorporation into bone hydroxyproline was increased in rats fed low calcium diet, in rats treated with parathyroid extract for 20 days, and in acutely thyroparathyroidectomized rats. In each instance, calcitonin prevented or reduced this increase. The results are interpreted as evidence that, with the doses used, hydroxyproline synthesis under normal conditions is unaffected by the hormone. However, where hydroxyproline formation was increased, calcitonin reduced this increase.

Rat glomerular basement membrane composition and metabolism in aminonucleoside nephrosis.

Abstract Rats treated with aminonucleoside of puromycin had a significant increase in incorporation of 3 H-proline and conversion to 3 H-hydroxyproline in glomeruli and glomerular basement membrane with the onset of proteinuria. There were no significant changes in the specific activity of hydroxyproline in bone or urine at any time during the course of the disease. The half-life of glomerular hydroxyproline measured 48 to 192 hours after the administration of 3 H-proline was 15 days. Two per cent of glomerular basement membrane hydroxyproline was solubilized by dilute acid and in this fraction the specific activity of hydroxyproline was higher than whole glomerular basement membrane. No changes in dilute acid solubility or amino acid composition of glomerular basement membrane were seen in aminonucleoside-treated animals with proteinuria.

PARATHYROID HORMONE AND EXPERIMENTAL OSTEOSCLEROSIS

Tests were done in growing rats to see whether the osteosclerotic changes provoked by parathyroid extract could be due to a compensatory secretion of calcitonin. Parathyroid extract increased metaphyseal bone in both intact and thyroparathyroidectomised animals. Likewise, peptide-pure parathyroid hormone induced similar changes in thyroparathyroidectomised rats. Incorporation of 3H-proline into bone hydroxyproline in these animals was strikingly augmented. It is concluded that (1) parathyroid-extract-induced osteosclerosis is not due to compensatory changes in calcitonin secretion; (2) parathyroid hormone itself, and not a contaminating peptide, is the cause; and (3) parathyroid hormone induces osteosclerosis by increasing bone formation, unlike calcitonin which does so by inhibiting bone resorption.