Osteolytic Activity and Reversal of Nephrectomy-Induced Hypocalcemia by a Fraction other than 1,25(OH)2-Vitamin D3fromSolanum MalacoxylonIncubated with Ruminal Fluid

Abstract

Previous studies have shown that two lipid soluble fractions (2 and 3) isolated from Solanum malacoxylon leaf extracts incubated with ruminal fluid by Sephadex LH-20 chromatography increase intestinal P absorption and blood Ca. Fraction 2 contains 1,25(OH)2-vitamin D3, vitamin D3, 25(OH)-vitamin D3 and 1,24,25(OH)3-vitamin D3. The osteolytic activity and ability to revert nephrectomy-induced hypocalcemia of fractions 2 and 3 was compared. The tibias from 19-day-old chick embryos injected with both fractions on day 15 were shorter, lighter and had a lower ash content than those from controls. Fractions 2 and 3 also decreased dry weight and ash content in frontal bones, although only the effects of fraction 3 were statistically significant. In agreement with these observations, fraction 3 was more effective than fraction 2 to increase blood Ca levels in nephrectomized rats. Extracts from rumen samples were devoid of activity. The results support the presence of a polar derivative of 1,25(OH)2D3 in ruminal fluid-treated Solanum malacoxylon.