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Effects of temperature and inorganic ions on calcium accumulation in microsomes from intestinal smooth muscle (1975)

Hurwitz, Leon ; Debbas, Gamil ; Little, Sally

Springer

Molecular and cellular biochemistry 8 (1975), S. 31-41

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ISSN: 1573-4919

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Summary Energy dependent calcium binding in microsomal vesicles from the longitudinal smooth muscle of the guinea pig intestine was investigated at two different temperatures (30 °C and 10 °C) and in the absence and presence of CdCl2, BaCl2 and MnCl2. The investigation was carried out to determine whether the effects of temperature and the effects of the divalent ions on microsomal calcium binding could be correlated with the effects of these interventions on the mechanical activity of the intact longitudinal fibers. A reduction in temperature from 30 °C to 10 °C inhibited both the uptake of calcium into the microsomes and the rate of release of calcium ions from the microsomes to the external medium. This change in temperature also slowed the rate of relaxation of the intact longitudinal muscle after it had been induced to contract with acetylcholine and subsequently allowed to relax by removing calcium ions from the bathing medium and adding 1 Ø 10−3 m EGTA. The presence of CdCl2, like the reduction in temperature, decreased the uptake of calcium into the microsomal vesicles. However, the release of calcium from the microsomes was accelerated. BaCl2 produced the same effects as did CdCl2 on the uptake of calcium into microsomes but to a lesser extent. It had very little effect on the release of calcium ions from the microsomes. MnCl2 had no significant effects on either the uptake or release of calcium ions in the microsomal preparation. Both CdC12 and MnCl2 exerted an inhibitory action on acetylcholine-induced contractile responses of the intact longitudinal fibers; whereas BaCl2 served to initiate a contractile response in the smooth muscle fibers. Thus, it would appear that the effects of a temperature change on microsomal calcium binding and on mechanical activity in intact fibers can be correlated; but the effects of CdCl2, BaCl2 and MnCl2 on these two cellular processes do not follow any consistent pattern.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01731647

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Electron microscopic localization of calcium in vascular smooth muscle (1975)

Debbas, Gamil ; Hoffman, Loren ; Landon, Erwin J. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

The @Anatomical Record 182 (1975), S. 447-471

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ISSN: 0003-276X

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: Potassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of the isolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaCl2 to the incubation medium results in welllocalized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contractionrelaxation cycle of vascular smooth muscle.

Additional Material: 2 Tab.