Plasma levels of growth hormone, corticosterone and insulin, during induced hepatocyte synchronization in young rats.
A wave of synchronous hepatocytes entering the cell cycle can be obtained in vivo after a subcutaneous injection (e.g. of casein) in rats at around Post-natal Day 10, when plasma growth hormone (GH) levels reach a low plateau (40 +/- 2 ng/ml) and liver cell proliferation rate is high. The present work reports the following changes in plasma hormone concentrations after synchronization of 20% of the hepatocyte population: (1) during the G1 phase (i.e. 6-12 hr after the mitogenic trigger), plasma GH concentration has dropped further (25 +/- 1.5 ng/ml). It was back to 90% of control levels during the S phase, mitosis and the following response including a transitory decrease in labelling index below control values. Injected together with the irritating mitotic trigger, a single dose of rat GH reduced the cell synchronization and post-synchronization effects by 50%. (2) Plasma corticosterone levels varied inversely to those of GH, increasing to twice the control values during G1 and were back to physiological levels when synchronized hepatocytes entered the S phase. (3) Variations in insulin levels were similar to that of corticosterone, with narrower ranges and reduced amplitudes. Our data suggest a possible correlation between the observed variations in plasma hormone levels and the induced synchronous hepatocyte response.
D000818:Animals; D000831:Animals, Newborn; D002364:Caseins / Q000494:pharmacology; D002453:Cell Cycle; D003345:Corticosterone / Q000097:blood*; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D007328:Insulin / Q000097:blood*; D008099:Liver / Q000166:cytology*; D008297:Male; D051381:Rats
D002364:Caseins; D007328:Insulin; D013006:Growth Hormone; D003345:Corticosterone