title: Influence of PLC and MLCK inhibitors and the role of L-calcium channels in the cat pulmonary vascular bed.
abstract: The effects of U-73122, a phospholipase C (PLC) inhibitor, on pressor responses to angiotensin II (ANG II), norepinephrine (NE), serotonin (5-HT), BAY K 8644, and the thromboxane A2 (TxA2) mimic, U-46619, were studied in the pulmonary vascular bed of the intact-chest cat. Under conditions of constant lobar blood flow, injections of ANG II, NE, 5-HT, U-46619, and the calcium channel opener, BAY K 8644, into the lobar arterial perfusion circuit caused dose-related increases in lobar arterial pressure, which were reproducible with respect to time. Infusion of U-73122, a PLC inhibitor, into the perfused lobar artery at 10-100 micrograms/kg for 10 min significantly reduced responses to ANG II, serotonin, and NE; however, U-73122 did not alter responses to BAY K 8644 or to U-46619. In a separate series of animals, the effects of the myosin light chain kinase inhibitor, KT-5926, were investigated, and after infusion of KT-5926 into the perfused lobar artery at 1-2 micrograms/kg for 10 min, responses to ANG II, NE, 5-HT, BAY K 8644, and U-46619 were reduced significantly. In a final series of experiments, the effects of the L-type calcium channel blocker, nicardipine, were investigated, and infusion of the L-type calcium channel blocker into the perfused lobar artery at 0.5-1 microgram/kg for 10 min reduced responses to ANG II, BAY K 8644, and NE. However, nicardipine did not alter pressor responses to 5-HT or the TxA2 mimic, U-46619.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001808:Blood Vessels / Q000187:drug effects / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002227:Carbazoles; D002415:Cats; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D007211:Indoles; D008297:Male; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D009529:Nicardipine / Q000494:pharmacology; D011652:Pulmonary Circulation / Q000187:drug effects; D011760:Pyrrolidinones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002227:Carbazoles; D004963:Estrenes; D007211:Indoles; D011760:Pyrrolidinones; D014662:Vasoconstrictor Agents; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C063769:KT 5926; D009529:Nicardipine; D009219:Myosin-Light-Chain Kinase; D010738:Type C Phospholipases