Effects of External Calcium and Some Metabolic Inhibitors on Barium-Induced Tension Changes in Guinea Pig Taenia Coli

Abstract

It was reported that the contractions in taenia coli induced by carbachol (1), ACh (2), phosphatidic acid (3) and high-potassium (K) (1,4,5) are all dependent on external calcium.On the other hand, Yukisada and Ebashi (6) have reported that rat, guinea pig, and rabbit ileum and rat uterus respond to barium (Ba) in the absence of external cal cium. These results have been supported by experiments with rat uterus (7).In the first series of experiments in this paper, the relationship between Ba-induced tension development and external calcium was re-examined using isolated taenia coli preparations.K-induced contracture in taenia coli was reported to be composed of two phases, namely, phasic and tonic responses (5, 8). Furthermore, the tonic response was abolished in the presence of various inhibitors of metabolism and active transport (8).The second series of experiments were designed to examine the effect of the above mentioned inhibitors on Ba-induced tension development.Some of the results have already been reported (9). METHODSStrips of taenia coli were isolated from male guinea pigs and suspended in Tyrode solution of the following composition (in mm): NaCI, 136.8: KCI, 2.7: CaCl2j 2.5; MgC12, 1.0; NaH2PO4j 0.4; NaHCO3, 11.9; and glucose, 5.5. The medium was continuously aerated with 95% 02 and 5 % CO, and maintained at a temperature of 37°C.Tension changes in the smooth muscle preparations were recorded isometrically. Apparatus and procedure in these experiments were the same as those described in previous report (10).In the case of anoxia, 95% 02 of the gas mixture was replaced by 95% N2 gas. The Li-Tyrode solution was prepared by substituting NaCI in Tyrode solution with LiC1 in equivalent millimolarity.K-induced contracture was induced by the addition of 40 mm KCI in Tyrode solu tion without any subtraction of NaCI.

The effect of drugs on the constriction of isolated depolarized blood vessels in response to calcium or barium

“…The store of membrane-bound calcium which is involved is lost at a very slow rate during treatment with a calciumfree depolarizing solution. Similar findings have been reported recently by Karaki, Ikeda & Urakawa (1967) and Hotta & Tsukui (1968).…”

Movements of Calcium During Tension Development Induced by Barium and High-Potassium in Guinea Pig Taenia Coli

“…Although both concentrations of Ba induced tension development, the one induced by 0.5 mm Ba became irregular and that induced by 20 mm Ba gradually decreased with time. These results are the same as in a former report (1).…”

“…As this juncture a similarlity in the "early (phasic) phase" of both Ba and high-K induced tension development has to be considered. Both Ba and high-K produce a phasic contraction which is independent of metabolism (1,3,10). This process is as a result of release of Ca from a cellular site in the case of high-K as shown in the present and other data (3), but in the case of Ba induced phasic contraction the possibility of the existence of two processe has to be reckoned with, 1) a movement of Ca within the cell as in the case of high-K in the absence of metabolic energy and 2) an increased Ca exchangeability when energy is available.…”

“…In previous publications it was reported that barium in concentrations from 0.5 to 20 mm induced tension development in isolated guinea pig taenia coli, which response was dependent on the presence of external calcium (1), and that total Ca content did not change but 45Ca uptake of the cellular fraction which did not exchange within 4 minutes increased above control level during Ba-induced tension development (2). It was also mentioned that Ba increased Ca entry in taenia coli and that this Ca probably plays an essential role during tension development (2).…”

A Newly Isolated Antispasmodic—butylidenephthalide—

“…From evidence obtained in uterine tissue (10), it has been pointed out that ACh owes its spasmogenic effects on certain smooth muscle at least in part to a depolarizing action accompanied by an influx of extracellular calcium into the contractile cell. Furthermore, many authors suggest that barium produces its spasmogenic effects primarily by releasing bound calcium from intracellular storage pools (11)(12)(13)(14)(15). In addition, Van Breemen et al suggested that NE initiates aortic contractions by releasing intracellularly sequestered calcium (16).…”