Free cytosolic calcium during spontaneous contractions in smooth muscle of the guinea-pig mesotubarium

Himpens, B (author)

Lydrup, M L (author)

Hellstrand, Per (author): Lund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups

Casteels, R (author)

(creator_code:org_t)

Related links:: http://dx.doi.org/10...; show more...; https://lup.lub.lu.s...; https://doi.org/10.1...; show less...

Abstract Subject headings

The free intracellular calcium ion concentration ([Ca2+]i) was measured simultaneously with isometric force in strips of guinea-pig mesotubarium using the Fura-2 technique. During the relaxed period (5-15 min) between spontaneous contractions [Ca2+]i continues to decrease after full mechanical relaxation to reach a minimal level of 86 +/- 8 nM (n = 9) just before the start of the next contraction. During the spontaneous contractions (5-15 min) [Ca2+]i reached a maximum of 211 +/- 19 nM and then oscillated between 155 +/- 16 nM and 194 +/- 9 nM. Increased extracellular Ca2+ concentration to 10 mM from the standard concentration of 1.5 mM caused a decreased frequency of spontaneous contractions and an increase in [Ca2+]i both in the relaxed and contracted states. In 10 mM extracellular Ca2+, addition of AlF4-, as 1 mM NaF + 10 microM AlCl3, caused a sustained increase in [Ca2+]i and maintained force. Addition of verapamil (10 microM) in this situation decreased [Ca2+]i to the resting level. The results suggest that the cyclic appearance of trains of action potentials is related to variation in [Ca2+]i, possibly via inactivation of Ca2(+)-dependent K+ channels.

About the subject

MEDICAL AND HEALTH SCIENCES: MEDICAL AND HEAL ...; and Basic Medicine; and Physiology

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