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Postnatal changes in T‐type calcium current density in rat atrial myocytes.
Author(s) -
Xu X,
Best P M
Publication year - 1992
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 - 10.1113/jphysiol.1992.sp019285
Subject(s) - medicine , endocrinology , myocyte , electrophysiology , chemistry
1. Postnatal changes in Ca2+ current were studied in voltage clamped atrial myocytes isolated from Sprague‐Dawley rats. T‐ and L‐type Ca2+ currents were identified using standard electrophysiological and pharmacological techniques. Cells were studied from seven groups of male and six groups of female rats ranging in age from 3 to 14 weeks. 2. The density of atrial T‐type Ca2+ current showed significant variation during postnatal development, with a maximum density reached at 4.5‐5 weeks. At this age, T‐current density was 1.44 +/‐ 0.11 pA/pF (n = 23) for cells isolated from male and 1.25 +/‐ 0.09 pA/pF (n = 25) for cells isolated from female animals in bathing solutions containing 2 mM‐Ca2+. T‐current density in atrial cells isolated from younger animals (3.5 weeks postnatal) averaged 1.22 +/‐ 0.06 (n = 18) and 1.00 +/‐ 0.05 pA/pF (n = 22) or 85 and 80% of the maximum seen at 4.5‐5 weeks for male and female rats, respectively. For rats older than 13 weeks, the average T‐current density in atrial cells was 0.50 +/‐ 0.03 (n = 18) and 0.51 +/‐ 0.02 pA/pF (n = 35) or 35 and 41% of the maximum seen at 4.5‐5 weeks for male and female rats, respectively. 3. In contrast to the T‐type current, the density of atrial L‐type Ca2+ current remained unchanged in rats from 3 to 14 weeks old. L‐type current averaged 8.2 +/‐ 0.2 (n = 134) in male and 7.9 +/‐ 0.2 pA/pF (n = 102) in female rats. 4. Fluctuation analysis was used to estimate single T‐channel current levels in 4.5‐ and 7.5‐week‐old male rats. While the T‐current density differed by 70% at these two postnatal ages, no significant difference (P > 0.2) in single channel current was found. Single channel current was 0.12 +/‐ 0.01 pA (n = 9) for cells from 4.5‐week‐old and 0.13 +/‐ 0.01 pA (n = 7) for cells from 7.5‐week‐old rats. Currents were stimulated by test pulses from ‐80 to ‐30 mV at 5 mM‐Ca2+. 5. No postnatal changes were seen in either the kinetics of activation or inactivation of macroscopic T‐current.(ABSTRACT TRUNCATED AT 400 WORDS)