Effects of Bovine Growth Hormone on the Retarded Cerebral Development Induced by Neonatal Hydrocortisone Intoxication

Abstract

In comparison with normal controls, hydrocortisone-intoxicated rats (HC rats) had smaller cerebra, lowered 2'',3''-cyclic nucleotide 3''-phosphohydrolase (CNPase) activity and reduced learning ability. The reduction in cerebral weight and DNA content was caused by a decreased number of proliferating glial cells, because the usual postnatal elevation of thymidine kinase (TK) activity was suppressed in the cerebra from HC rats. EM observation of the pituitary gland revealed that the 5-day-old HC rat contained growth hormone (GH) secretory cells which were fully packed with GH granules, suggesting a disorder in the system which released GH. In an attempt to promote cerebral development in the HC rats, bovine GH (bGH) was given to some HC rats daily from the day of birth until weaning (HC + bGH rats). In the HC + bGH rats, cerebral DNA was restored to normal levels and a concomitant increase in TK and CNPase activity was noted. In the brightness discrimination test, whereas the HC + bGH rats attained the learning ability of normal controls after 10 sessions, HC rats were unable to reach an equivalent level even after 25 sessions.