Metabolic differences between norepinephrine- and K+-stimulated anococcygeus muscle.
The effects of norepinephrine (NE) and K+ stimulation on aerobic glycolysis (JLac), O2 utilization (JO2), and isometric force of isolated rat anococcygeus smooth muscle were investigated to determine the relationship between metabolism and contractility. A large sustained increase in JLac was measured during NE stimulation, but only a small rise in JLac occurred during high-KCl depolarization. JO2, in both cases, correlated with the force response. The difference in JLac could not be explained solely on the lower force output of K+-depolarized muscles or on increased glycogenolysis during NE stimulation, but was perhaps due to activation of energy-requiring processes associated with receptor- rather than depolarization-mediated Ca2+ mobilization. When muscles were stimulated with a K2SO4 (substituted for NaCl) Krebs-Ringer bicarbonate (KRB) rather than a N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered medium, JLac was significantly elevated due to an increased intracellular pH as a result of the low external Cl-. Lowering the pH of KRB or adding the anion exchange inhibitor 4-4'-diisothiocyanostilbene-2,2'disulfonic acid prevented the rise in JLac and also restored the initial fast component of the force response to NE in Cl(-)-free solution.
D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D010101:Oxygen Consumption; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D013268:Stimulation, Chemical; D013997:Time Factors
D002021:Buffers; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine