Peripheral circulating insulin-like growth factor-I and -II in cattle

Interrelationships between circulating concentrations of the insulin-like g rowth factors (IGF-I and IGF-II) were investigated in 235 blood samples tak en from 145 healthy beef or dairy calves, bulls and cows of different breed s and ages. Autoradiography of Western ligand blots indicated different IGF binding protein (IGFBP) profiles between sera from different categories of cattle. Each IGF radioimmunoassay was Validated by determining the effects of IGFBPs, ligand and contraligand, as well as serial dilution and compari son with results obtained after molecular sieve chromatography in acid. In female cattle mean values for IGF-I varied from 5.1 nmol/l in postparturien t Holstein cows to 18.5-20.5 nmol/l in growing beef heifers, while mean IGF -II concentrations ranged from 30.0 nmol/l in the cows to 14.7-15.7 nmol/l in the beef heifer calves. In male cattle mean serum IGF-I ranged widely fr om 8.2 nmol/l in 1-day-old Holstein carves to 67.4 nmol/l in 16-month-old S immental-type bulls. Mean IGF-II concentrations decreased from 22.9 nmol/l in 1-day-old Holstein bull carves to 11.9 nmol/l in 12-month-old beef bulls . Thus, total molar IGF concentrations were fairly stable in female cattle (24.7-35.1 nmol/l) but extended from 27.3 nmol/l to 81.8 nmol/l in the male cattle. The tendency for a reciprocal relationship between serum concentra tions of these growth factors was most obvious in the periparturient cows.