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Keywords:

Age Factors, Animals, Bone and Bones, Calcitriol, Calcium, Dietary, Calcium-Binding Proteins, Diabetes Mellitus, Female, Lactation, Osteocalcin, Phosphates, Pregnancy, Pregnancy in Diabetics, Rats, Rats, Inbred Strains, Reproduction, Science & Technology, Life Sciences & Biomedicine, Endocrinology & Metabolism, 0702 Animal Production, 0707 Veterinary Sciences, 1103 Clinical Sciences, 3003 Animal production, 3202 Clinical sciences

Abstract:

Concentrations of osteocalcin were measured in plasma and bone of normal and diabetic rats during the reproductive cycle and compared with plasma 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) concentrations. The age-dependence of osteocalcin was also examined. Plasma concentrations of osteocalcin levels were low but detectable in 21-day-old fetuses (3.7 +/- 0.3 nmol/l); osteocalcin concentrations were highest in weaning rats (104 +/- 9 nmol/l) and decreased thereafter. In adult rats, plasma concentrations of both osteocalcin and 1,25-(OH)2D3 increased during the last days of normal pregnancy, and even more so in rats fed a diet low in calcium and phosphate. After an early post-partum decline, osteocalcin concentrations in plasma remained at non-pregnant levels in lactating rats fed a high calcium/phosphate diet while their 1,25-(OH)2D3 concentrations were higher than in non-pregnant rats; however, lactating rats fed a low calcium/phosphate diet showed increasing osteocalcin concentrations. In spontaneously diabetic BB rats, plasma osteocalcin concentrations were severely decreased compared with those in non-diabetic rats, more than would have been expected from their decreased 1,25-(OH)2D3 concentrations. Moreover, plasma osteocalcin did not increase during pregnancy or lactation in diabetic rats, even when fed a low calcium/phosphate diet. Fetuses of diabetic rats also had lower plasma osteocalcin levels than fetuses from non-diabetic rats or than weight-matched fetuses from semistarved rats. In contrast to plasma osteocalcin concentrations, bone osteocalcin concentrations and content were not altered by pregnancy, lactation, low calcium/phosphate diet or diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)