Osteocalcin during the reproductive cycle in normal and diabetic rats |
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Authors: | J Verhaeghe E Van Herck R Van Bree F A Van Assche R Bouillon |
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Institution: | Laboratory for Experimental Medicine and Endocrinology, Catholic University of Leuven, Belgium. |
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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) |
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