Proteinous Amino Acids in Muscle Cytosol of Rats' Heart After Exercise and Hypoxia

Abstract

Levels of 19 proteinous amino acids and of total free amino acids were assayed by gas-liquid chromatography in cytosols of rat atrial and ventricular heart muscle cardiomyocytes. These amino acids were assayed after the rats had been exposed to either exercise (swimming) or hypoxia (hypobaric pressure of 686 hectoPascals). Out of the total free amino acids levels of arginine, glutamine and cysteine in atrial and ventricular cardiac muscle cytosols of control rats were the highest of all amino acids assayed. The control levels of all other amino acids assayed in atrial or ventricular cardiac muscles ranged from 0.1% to 10.6% of the total free amino acids in the control rats. Physical stress (exercise and hypoxia) significantly reduced the total amount of cytosolic free amino acids in both heart muscles. While hypoxia decreased the levels of arginine in both heart muscles, exercise abolished the level of cysteine in the atrial heart muscle. Decrease in arginine levels, and elimination of cysteine from the heart's atrial muscle after physical stress, may be attributed to its utilization of nitric oxide and to its synthesis of atriopeptin and/or endothelin during stress. No change was recorded in either experimental group in the level of glutamine in heart muscle cytosol. Exercise and hypoxia affect, in different modes, the levels of all other amino acids assayed, except for tryptophan, tyrosine, and histidine, which are precursors of endogenous neurotransmitters. The impact of proteinous amino acids on some bodily functions is discussed.

Proteinous Amino Acids in Hearts' Muscle Cytosol of Rats Pretreated with Digoxin, Caffeine or Isoproterenol

“…Propranolol and pentylenetetrazol decreased the 91 level of cysteine. We confirmed these results in another study (Gabrys et al 2003).…”

“…It was demonstrated that both physical stress and the three drugs, affected the levels of proteinous amino acids, mostly cysteine, arginine, histidine, isoleucine, alanine and tyrosine (Gabrys et al 2003(Gabrys et al , 2004.…”

Proteinous Amino Acids in Muscle Cytosol of Rats' Heart, After Their Treatment with Propranolol, Pentylenetetrazol or Reserpine

“…Similar decrease in ventricular L-arginine was observed in rats after hypoxia stress (Gabrys et al 2003) It is suggested that administration of these drugs, and hypoxia, enhance the release of agents such as endothelin and/or oxygen-derived free radicals, that in turn increase the production of endogenous NO and consequently decrease muscle-cytosol levels of L-arginine, its endogenous donor (Mullane et al 1987;Vane and Botting 1993). It was also suggested that NO prevents the intensive cardiac stimulation, as it is involved in the negative chronotropic effect of endothelium in the heart muscle (Zhu et al 1997).…”

“…In previous studies we have demonstrated that exercise completely abolished, while hypoxia decreased the levels of cysteine in the atrial heart muscle cytosol (Gabrys et al 2003). As exercise is a most stressful procedure, we believe that in the present study all the cysteine from the atrial cytosols turned into atriopeptins.…”

“…In another recent paper we studied the effect of exercise (swimming for four hours) and hypoxia (686 hectoPascals for four hours) on 19 proteinous amino acids in the cardiac muscle cytosol of rats (Gabrys et al 2003), and noticed that both physical stressors affect the levels of some amino acids, mainly arginine, cysteine, tryptophan, tyrosine and histidine…”