Effects of experimental phosphate deficiency on action potential characteristics and contractile performance of rat myocardium

• Published in: Cardiovascular research Vol. 16; no. 2; pp. 71 - 79
• Main Authors: CAPASSO, JOSEPH M, ARONSON, RONALD S, STROBECK, JOHN E, SONNENBLICK, EDMUND H
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.02.1982
• Subjects: Action Potentials; Animals; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Heart; Heart - innervation; Heart - physiopathology; In Vitro Techniques; Myocardial Contraction; Papillary Muscles - innervation; Papillary Muscles - physiopathology; Phosphates - blood; Phosphates - deficiency; Rats; Rats, Inbred Strains; Vertebrates: cardiovascular system; Heart; Phosphates; Rat; Papillary muscle; Rodentia; Electrophysiology; Action potential; Heart ventricle; Muscle contraction; Left ventricle; Vertebrata; Mammalia; Hypophosphatemia
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1093/cvr/16.2.71

Chronic hypophosphataemia is associated with reversible depression in myocardial performance of the intact heart. To define the basis for this, we studied the mechanical and electrical properties of isolated left ventricular papillary muscles from rats with 6 weeks of phosphorus depletion (P6), 6 weeks of phosphorus repletion and age-matched controls (C). Muscles were perfused with Tyrode's solution (Ca2+ = 2.4 mmol·litre−1, K+ = 4.0 mmol·litre−1, dextrose = 5.5 mmol·litre−1) and driven at 0.1 Hz. P6 muscles had slowed isometric relaxation (T1/2R), depressed velocity of shortening and relaxation and prolongation of the transmembrane action potential to 75% of complete repolarisation. These results suggest that the slow relaxation phase may be the result of the prolonged APD75 and that the depressed myocardial performance in the intact heart may be based on impaired relaxation and reduced the velocity of shortening associated with hypophosphataemia. This view is supported by our finding that these alterations are reversible with phosphate repletion.