Effects of Ouabain and 2,4-Dinitrophenol on Calcium Distribution and Exchange in Guinea Pig Taenia Coli in High-Potassium Solution

Abstract

Previous studies have shown that Ca influx increased but Ca efflux did not change during the contracture of taenia coli induced in hypertonically added 40 mm potassium solution (1) and the results were supported by the others (2-6). Further, the movements of Ca in the muscle in high-K solution might be differently affected by ouabain and 2, 4-dinitrophenol during the abolition of the tonic tension by them (6, 7).The experiments reported here were carried out in purpose to find the nature of Ca distribution and exchange in guinea pig taenia coli in high-K solution using ouabain and 2, 4-dinitrophenol. METHODSStrips of taenia coli isolated from white male guinea pigs were suspended in an organ bath containing Tyrode solution of the following composition (mm); NaCI 136.8, KCl 2.7, CaC1, 2.5, MgCl2 1.0, NaH2PO4 0.4, NaHCO, 11.9 and glucose 5.5, saturated with 95% 02 and 5% CO, mixture at 37'C. Isotonically added 40 mm K solution (iso-40 K-S.) was made by replacing 40 mm NaCI in Tyrode solution with equimolar KC1. Tension changes were isometrically recorded with a mechanoelectro-transducer. 45Ca uptake: After pretreatment , muscle strips were soaked in iso-40 K-S. for 30 minutes, then 2.5 x 10-6 M ouabain or 1 x 10-4 M 2, 4-dinitrophenol (DNP) was added. Thirty minutes after the addition of ouabain or DNP, corresponding to zero time of Fig. 1, 45Ca (1 x 106 counts/min-ml) was added to the medium for incubation. After 5, 15 or 30 minutes incubation period, the strips were removed from the bath and radioactivities in the muscle strips were counted (1, 4). Tissue Ca: Strips were treated in the same manner as that in the preceding para graph except that 45Ca was not used and Ca content of the tissue was determined using atomic absorption spectrophotometer (1, 4). 45Ca efflux: Muscle strips were incubated in iso -40 K-S. with 45Ca (200 pCi/ml) for 180 to 200 minutes and then washed by dipping into successive tubes containing iso

Effect of Histamine on Calcium Movement in Guinea Pig Taenia Coli

“…on the smooth muscles in the presence of various stimulants and relaxants. However, the presence of the correlation between tension development and the size of TBF has al ready been suggested (3)(4)(5) and the present data also supports this.…”

“…However, as reviewed by L&uuml;llmann (1), no correlation has been found between tissue Ca content or Ca fluxes and the contractile response of the smooth muscle to various stimu lants.<BR> In guinea pig taenia coli, it was shown that cellular Ca fraction of relatively tightly bound form increase during contraction induced by barium or high concentration of potas sium and decreased during the abolition of tension development by various inhibiting factors, and suggested that the shift of Ca into the relatively tightly bound fraction with in the cell might have a concern with the tension development (2)(3)(4)(5).<BR>…”

Effects of ouabain on high-K induced contractions of various smooth muscle tissues in the guinea-pig.

“…Previous studies have shown that the tonic contraction produced by a high-K solution is inhibited by ouabain in the guinea-pig taenia coli (2,(19)(20)(21)(22)(23)(24) and ileum (25). In the present paper, we have found that the effects of ouabain on K-contraction are different in several smooth muscle tissues isolated only from the guinea-pig.…”

A Shift of Cellular Calcium to a More Slowly Exchangeable Fraction During Contraction in Guinea Pig Taenia Coli

“…The size of TBF increased during tonic contraction induced by carbachol, pilocarpine (3), histamine (4), barium (5) and 40 mM potassium (5,6), and decreased during abolition of tension by specific antagonists oft he stimulants (3,4), metabolic inhibiting factors and factors inhibiting active Na transport (8,9). from these data., it was suggested that the increase in the size of TBF, i.e., a shift of cellular Ca to a more slowly exchangeable fraction, could be related to contraction of smooth muscle, and the movement of Ca related to metabolism.<BR>…”