Growth and Lactogenic Hormone Stimulation of Ornithine Decarboxylase in Neonatal Rat Brain*

Bovine growth hormone (bGH), bovine prolactin (bPRL), human placental lactogen (hPL) and nerve growth factor (NGF) were administered intracisternally (ic) and intraperitoneally (ip) to 16–18-day-old rats, and ornithine decarboxylase (ODC) activity in brain and liver was determined. All four hormones stimulated brain ODC activity when injected ic: bGH caused a 458% increase of activity compared to controls while bPRL, hPL and NGF were about half as potent as bGH. When injected ip, bGH and bPRL, but not hPL or NGF, stimulated brain ODC activity. bGH and bPRL, but not hPL, stimulated liver ODC activity after both ic and ip administration. A fragment derived from bGH by cleavage with cyanogen bromide (fragment A) had 40% of the activity of intact bGH on brain ODC activity when given ic. The results suggest that GH may be involved in the regulation of CNS development through its effects on polyamine synthesis. The finding that when injected intracisternally hPL and NGF, as well as bGH and bPRL, are capable of increasing brain ODC activity but when administered systemically only bGH and bPRL are active suggests significant differences in the ability of these hormones, or their derivatives, to penetrate the blood-brain or blood-CSF barrier. (Endocrinology95: 904, 1974)