Interrelation among endogenous catecholamines, prostaglandin F2 alpha and prolactin in last trimester and during...

To investigate the interrelation among endogenous catecholamines, prolactin and prostaglandin F2 alpha, we measured the plasma levels of dihydroxyphenylalanine (DOPA), norepinephrine (NE), catecholamine metabolites (3,4-dihydroxyphenylacetic acid [DOPAC], 3,4-dihydroxyphenylethyleneglycol [DOPEG], cyclic 3',5'-adenosine-monophosphate (c-AMP), prostaglandin F2 alpha (PGF2 alpha) and prolactin (PRL) in 119 patients, before, during and after a normal labor and delivery, and in the early puerperium. In late pregnancy, DOPAC concentrations were significantly increased, and reached peak values before the onset of labor in the group who went into spontaneous labor. The DOPA, NE and DOPEG levels remained unchanged before labor. The plasma concentrations of NE, c-AMP and PGF2 alpha were significantly increased during labor. There was a positive correlation between plasma NE and c-AMP (r = 0.584, p less than 0.001), and between NE and PGF2 alpha (r = 0.401, p less than 0.001) during labor. In contrast, plasma PRL significantly decreased during labor and immediately after delivery. There was a statistically significant inverse relationship between PRL and NE (r = -0.392, p less than 0.001) and between PRL and PGF2 alpha (r = -0.523, p less than 0.001) during labor, but there was no statistical correlation among PRL, DOPA and DOPAC. In conclusion, these data suggest that the dopaminergic activity in the maternal circulation increases before the onset of labor, and the PRL release from the maternal pituitary gland during labor is probably not controlled primarily by dopaminergic neurons and may be suppressed by other mechanisms, such as the stress of labor and/or the influence of PGF2 alpha.