GTPase activity in mouse hippocampus membranes following prenatal exposure to heroin and phenobarbital.

Low Km high affinity GTPase activity, with and without muscarinic receptor stimulation with 1 mM carbachol, was measured in membrane preparations of mouse hippocampus prenatally exposed to phenobarbital or heroin. Basal and carbachol-stimulated low Km GTPase activities after prenatal exposure to phenobarbital exhibited a statistically significant (P < 0.05) decrease both in Km and Vmax values. Basal Vmax values were reduced from 152 +/- 10 in controls to 112 +/- 13 (pmol/mg protein/min, mean +/- SEM) in exposed mice. The Km values in the offspring of mice treated with phenobarbital were reduced from 1.55 +/- 0.21 to 0.96 +/- 0.11 (microM, mean +/- SEM); Vmax and Km values after carbachol stimulation were similarly affected. Prenatal exposure to heroin did not change the GTPase activities, basal or carbachol-stimulated, with only a non-significant increase in both Vmax and Km values. It is postulated that these changes in G alpha protein activity may be related to the teratogenic effect of these drugs.