45Ca UPTAKE AND TISSUE Ca OF GUINEA PIG TAENIA COLI IN ISOTONIC HIGH-K/Na-DEFICIENT MEDIUM

Abstract

It has already been reported that 45Ca uptake and total Ca content of guinea pig taenia coli increased when 40 mm K was added hypertonically to the external medium (1, 2).However, the addition of high-K isotonically, that is, an appropriate concentration of ex ternal sodium replaced by potassium, to depolarize and/or contract smooth muscle prepa rations, is the method that is widely employed.We have reported (3) that in isotonic high-K medium, which contained less Na, smooth muscle of taenia coli showed a shape of contracture different to that shown in hypertonic 40 mm K medium, which contained normal concentration of Na.In the present paper, changes in 45Ca uptake and tissue Ca of guinea pig taenia coli in isotonic 152 mm K/Na deficient medium were studied and the results were compared with those in hypertonic 40 mm K medium. METHODSStrips of taenia coli isolated from male guinea pigs were suspended in an organ bath containing Tyrode solution of the following composition (mm): NaCl, 136.8; KC1, 2.7; CaC12, 2.5; MgC1,, 1.0; NaH2PO4j 0.4; NaHCO3, 11.9; and glucose, 5.5, saturated with 95% 02 and 5% CO2 gas mixture at 37°C. Tension changes were recorded isometrically with Nihon Kohden multi-purpose polygraph.45Ca uptake: After pretrc ~tment , muscle strips were placed in an incubation medium containing 45Ca (1 x 106 counts ,' ainute) ml) for specified intervals with and without elevated K. At the end of each incubation period, the strips were washed three times in 4 minutes with a non-radioactive Tyrode solution of the same composition as the incubation medium, removed from the bath, blotted gently on filter paper and weighed. They were then transferred to quatz tubes to which 0.1 ml HC104 was added. The samples were ashed in a furnace at 550°C, diluted with 0.1 N HC1, pipcttcd into planchettes, dried and radio activity was counted in a gas flow counter (Aloka window type Model PS-13). Data are expressed as counts per minute per kilogram wet weight of muscle. Radioactive 45Ca was supplied by Nuclear Science and Engineering Corp., U.S.A., as the chloride.

EFFECTS OF OUABAIN AND METABOLIC INHIBITING FACTORS ON Ca DISTRIBUTION DURING K-INDUCED CONTRACTURE IN GUINEA PIG TAENIA COLI

“…The factors inhibiting the high-K induced tension, viz., ouabain, Li substitution, DNP, glucose removal and anoxia, decreased the increased size of TBF by high-K to the level in normal medium. These results confirm the suggestion that Ca fraction which did not exchange within 4 minutes (TBF) may be closely related to tension development in taenia coli (5,6,10,11). The increased tissue Ca in high-K medium was reduced by DNP, glucose removal and anoxia to the control level although ouabain and Li substitution did not significantly alter it (P<0.01).…”

Effects of Calcium Depletion on Oxygen Consumption in Guinea Pig Taenia Coli

“…Hence, there is some hesitation to refer to his results in Ca and Sr influxes. Urakawa et al found that taenia coli showed large tonic tension averaging 12 gin hypertonic 40 mm K medium (42.7 mm K, 149.1 mm Na) and tissue Ca of the muscle increased in the medium, while in isotonic 152 mm K medium (151.8 mm K, 0 mm Na) only a small tension about 2 g remained and "Ca uptake did not increase and tissue Ca decreased (16).…”

A comparative study of the contraction induced by high K/Na deficient solution in the trachea, gall bladder and urinary bladder in guinea-pig.

“…Hyperosmotically added K solution induced a sustained contraction, while isosmotically substituted high K, Na deficient solution induced a transient contraction in guinea-pig taenia coli (2)(3)(4) and rabbit aorta (6). However, a substituted high K solution induced a sustained contraction during 120 min in bovine (21) and monkey trachea (F. Ueda and N. Urakawa, unpublished data).…”