UBC Theses and Dissertations
Sodium transport across the locust rectum Black, Kenneth Thomas
It was the purpose of this study to further elucidate the movements of Na⁺ across the rectal epithelia of locusts, Schistocerca gregaria. The kinetics of ²²Na absorption are investigated yielding a K[sub m] of 17.2 mM and a V[sub max] of 1.54 u Eq cm⁻² h⁻¹. The effects of a stimulant (cAMP) and inhibitors (Amiloride and Ouabain) are also investigated. cAMP (1 mM) has no effect on ²²Na flux but does cause an increase in short-circuit current (I[sub sc] ) (1.28 ± 0.12 to 4.80 ± 0.28 uEq ⁻² h⁻¹) and potential difference (P.D.). (4.4 ± 0.3 to 13.2 ± 0.8 mV) at a Na⁺ concentration of 55 mM. Amiloride (1 mM) causes a 33% reduction of ²²Na influx and a 75% reduction of net ²²Na absorption by the recta. The inhibition caused by amiloride is reversible. Ouabain has no effect on ²²Na flux at room temperature (21 °C) but causes a 37% reduction of ²²Na influx (lumen to hemocoel) at 29°C. Ouabain and amiloride have no effect on I[sub sc] or P.D. Extracts from several neuroendocrine tissues had no conclusive effect on ²²Na fluxes as tested.
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