Localization of adenylate cyclase in myocardial junctional sarcoplasmic reticulum. Cytochemical study after isoproterenol activation and propranolol inhibition of beta receptors.
A method for preservation of both morphological and enzymatic integrity was used to demonstrate localization of adenylate cyclase (AC) in rat myocardium. Short prefixation with a 2% glutaraldehyde solution and 5% DMSO followed by incubation in modified standard medium with 10 mM ouabain, 1 mM adenine deaminase, and 1 mM tetramisol with 10-20 mM NaF and 0.1-0.4 mM isoproterenol as activators and/or 1-100 propranolol as a beta blocker allowed regularly reproducible localization of fine granular precipitate of lead imidodiphosphate at the sites of adenylate cyclase activity. In addition to localization on the sarcolemma, the greatest precipitation was found inside the junctional sacroplasmic reticulum and subsarcolemma cisternae. Longitudinal sarcoplasmic reticulum was free of precipitate. Participation of Ca2+ ions in these areas, where calcium is usually present in high concentration, was excluded by electron probe X-ray microanalysis. The amount of precipitate was greatly enhanced after stimulation of AC with isoproterenol or NaF and was diminished by 30-min preincubation with 10-100 mM propranolol.
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008870:Microtubules / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D011433:Propranolol / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000201:enzymology
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D000262:Adenylyl Cyclases; D007545:Isoproterenol