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DIFFERENCES IN THE CHARACTERIZATION OF THE Ca 2+ CURRENT IN VENTRICULAR MYOCYTES BETWEEN SPONTANEOUSLY HYPERTENSIVE RATS AND NORMOTENSIVE RATS
Author(s) -
Nakata Tomoe,
Sato Sadayuki,
Hachisu Mitsugu,
Tsutsumi Takeshi,
Osada Hirofumi
Publication year - 1995
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1995.tb02895.x
Subject(s) - medicine , cardiology , myocyte , chemistry , endocrinology
Summary 1. The slow inward Ca 2+ current elicited at the membrane potential ‐ 30 mV in SHR and normotensive Wistar rats (WR) with voltage‐clamp recording was examined for this study. 2. The maximal Ca 2+ current of WR in the current‐voltage relationship showed the unified membrane potential of + 10 mV and the amplitude was −1.2 ± 0.2PA. In the case of SHR, however, the maximal Ca 2+ current showed a lower and variable membrane potential between 0 and −20 mV. The amplitudes were −1.7 ± 0.9 pA at 0mV, −2.1 ± 0.8 pA at −10mV and −4.4 ± 0.3 pA at −20mV. 3. From the cell‐attached patch‐clamp recording, the conductance of unitary Ca 2+ current and the slope value were the same in SHR and in WR. From the open‐time histogram of the Ca 2+ channel, the open state probability in SHR increased and the time constant from the exponential curve became slightly extended in SHR. 4. L‐isoproterenol at 10 ‐6 mol/L increased the Ca 2+ current in SHR and WR. The increased ratio of Ca 2+ current by I‐isoproterenol was smaller in SHR than that in WR. 5. The aspect of 1–4 suggests that the increase in Ca 2+ current in SHR obtained by the voltage‐clamp was explained partly by the increase of open‐state probability of unitary Ca 2+ channel activity, and that a possibility of Ca +2 channel being activated by phosphorylation through cAMP did not eventuate.