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Age and gender differences in excitation‐contraction coupling of the rat ventricle
Author(s) -
Leblanc Normand,
Chartier Denis,
Gosselin Hugues,
Rouleau JeanLucien
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.533bh.x
Subject(s) - isometric exercise , medicine , ventricle , endocrinology , contractility , papillary muscle , contraction (grammar) , electrophysiology , chemistry , myocyte
1 The objective of this study was to determine potential post‐pubertal gender‐specific differences in the contractility of papillary muscles, the electrophysiological properties and Ca 2+ transients of freshly dissociated ventricular myocytes from the rat heart. 2 The contractions of rat papillary muscles from 2‐ to 14‐month‐old male and female rats were studied under isometric and isotonic conditions (29 °C). While the hearts of young (2–4 months) male and female rats displayed a similar contractile profile, papillary muscles of female rats aged 6 months and older exhibited smaller isometric and isotonic contractions, smaller maximal rates of tension and shortening development and decline (±D T /d t and ±D L /d t ) velocities during both the onset and relaxation phases, and shorter contractions than age‐matched males. 3 To explore the possible cellular basis accounting for these differences, action potentials and macroscopic currents were recorded from freshly dissociated myocytes using the whole‐cell patch clamp technique (35 °C). Action potentials from male and female myocytes of 3‐ and 9‐month‐old rats did not vary as a function of age or gender. Consistent with these results, the magnitude (expressed in pA pF −1 ), voltage‐dependence and kinetics of the inward rectifier ( I K1 ), transient outward ( I to ) and sustained ( I K ) K + currents displayed little, if any dependence on age or gender. 4 L‐type Ca 2+ current ( I Ca(L) ) measured in caesium‐loaded myocytes (35 °C) from male and female rats of 3, 6 and 9 months of age exhibited similar characteristics. In contrast, while Ca 2+ transients measured with indo‐1 were similar between 3‐month‐old male and female rat myocytes, Ca 2+ transients of 10‐month‐old female myocytes were significantly reduced and showed a diminished rate of relaxation in comparison with those recorded in male rats of similar age. 5 These results suggest that important gender‐related changes in excitation‐contraction coupling occur following puberty, probably due to differences in Ca 2+ handling capabilities at the level of the sarcoplasmic reticulum.