Does oral contraceptive (Enovid) treatment enhance renal hypertension in rats by inducing sympathetic hyperactivity?

One-kidney renal hypertension was induced in rats that had been given Enovid or corn oil by daily gavage for 5 weeks, and treatment was then continued postoperatively for 10 weeks more. Systolic pressures began to rise almost immediately after hypertension was induced, and from the 4th postoperative week on, the pressure elevation was consistently more pronounced in Enovid-treated than in corn oil-treated rats. When autonomic ganglia were subsequently blocked with mecamylamine, the ensuing blood pressure fall was invariably larger in Enovid-treated than in corn oil-treated rats. In contrast, responses to beta-adrenergic blockade with propranolol were equivocal; heart rates fell while systolic pressures rose slightly to about the same extent in both groups. The larger hypotensive response to ganglion blockade in Enovid-treated rats is in accord with the interpretation that Enovid treatment augments development of renal hypertension by increasing sympathetic vasomotor tone.