The production and secretion of cortisol by baboon neonates.

The metabolic clearance rate (MCR), transfer constants (p), production (PR) and secretion (SR) rates of cortisol (F) andrortisone (E) were determined by the continuous infusion of {1,2³H}F and {4-¹⁴C}E into 5 neonates delivered prior to the parturition by cesarean section (164–179 days; term = 184 days) and into 5 newborns delivered spontaneously per vagina at term (166 – 187 days). In spontaneously delivered animals, MCR-E (X ± SE, 34.3 ± 7.0 1/day/kg was greater (P < 0.001) than MCR-F (14.9 ± 1.5 1/day/kg), pF to E (59.7 ± 8.9%) exceeded (P < 0.001) pE to F (17.8 ± 3.0%) and the percentage of F bound to serum proteins other than albumin (57.5 ± 6.2) was greater (P < 0.001) than that of E (27.0 ± 10.3) Although the serum E level (25.6 ± 3.6 μg/100 ml) was similar to that of F (33.5 ± 8.0 μg/100 ml), the PR-E (6.4 ± 1.3 μ/min/kg) was greater (P < 0.001) than PR-F (3.3 ± 0.5 μ/min/kg). Approximately eighty-five percent of the E and 65% of the F produced orginated by secretion.In animals delivered by cesarean section, the serum F concentration (32.4 ± 6.7 μ/100ml), pE to F (13.4 ± 2.8%) pF to E (80.0 ± 12.2%) PR-E (4.5 ± 0.2 μ/min/kg) and SR-E (3.9 ± 0.3 μ/min/kg) were not different from values for spontaneously delivered animals. Serum E levels (35.9 ± 1.6 μ/100 ml) were higher but MCR-F (6.7 ± 0.6 1/day/kg) and MCR-E (18.2 ± 0.41/day/kg) lower in neonates delivered by cesarean section. Serum Cortisol binding capacity (μg F bound/100 ml) was greater (P < 0.025) in neonates delivered by cesarean section (23.6 ± 2.6) than in spontaneously delivered animals (14.4 ± 2.0). As a result of these changes in F and E dynamics, PR-F (1.4 ± 0.3 μ/min/kg) and SR-F (0.9 ± 0.2 μ/min/kg) in neonates delivered by cesarean section were lower (P< 0.01) than corresponding values in spontaneously delivered newborns.It is concluded that the greater F secretion in animals delivered spontaneously than those delivered by cesarean section probably results from increased fetal adrenal 3β-hydroxysteroid dehydrogenase-isomerase activity, which as previously reported, occurs in late gestation in this species.