Dopamine receptor blockade increases glandular kallikrein-like activity in the neurointermediate lobe of the rat pituitary.

The effect of dopamine receptor blockers on glandular kallikrein-like activity in the neurointermediate lobe of the rat pituitary was examined. Male rats were given daily injections of haloperidol (2.5 mg/kg), perphenazine (5 mg/kg) or sulpiride (60 mg/kg) for 7 days. Homogenates of the neurointermediate lobe were prepared. Latent proteases were activated with trypsin and proteolytic activity was measured at 37 degrees C, pH 8.0 using chromogenic peptide substrates. All three dopamine receptor blockers produced about a 100% increase in glandular kallikrein-like activity. The results suggest that glandular kallikrein-like activity in the neurointermediate lobe is under inhibitory control by dopaminergic mechanisms.