Developmental Profiles of Catecholaminergic Enzymes in Adrenals of Perinatal Rats: Effect of a Hypoxic Environment

Summary

Fetal and early neonatal development of adrenal catecholaminergic enzymes was studied in rats maintained under normal (normoxic) and high-altitude, 3800 m, 13 % PO₂ (hypoxic) conditions. In adrenals of normoxic fetuses, tyrosine hydroxylase (TH), DOPA-decarboxylase (DDC), phenyleth-anolamine-N-methyltransferase (PNMT), catechol-O-methyl-transferase (COMT) and monoamine oxidase (MAO) showed rapid increases in activity from day 19 to day 21 of gestation. The activities of all enzymes but TH were higher at day 1 postpartum compared to fetal values: TH was equiactive just before and after birth.

In animals conceived, born and raised at high altitude, several changes indicative of impaired adrenal development occurred. The activities of the synthesizing enzymes, TH, DDC and PNMT, were variably affected at some time during the perinatal period. The activities of the catabolizing enzymes, MAO and COMT, at high altitude were increased on the last days of gestation but depressed after birth, compared to control levels. Catecholamine content in high-altitude adrenals was altered on day 19 of gestation when epinephrine was lower, and again on day 1 postpartum when both norepinephrine and epinephrine were higher than in control adrenals at sea level. Normal developmental changes and high-altitude-induced disturbances in adrenal catecholaminergic enzymes are discussed with reference to differences observed in adrenal cortical function between sea-level and high-altitude animals.

Key-Words

Adrenal Gland - Development - Rat - Hypoxia - Tyrosine Hydroxylase - DOPA Decarboxylase - Phenylethanolamine-N-Methyltransferase - Catechol-O-Methyltransferase - Monoamine Oxidase - Norepinephrine - Epinephrine