The effect of the corpora cardiaca-corpora allata system on oxygen consumption in the cockroach rectum: The role of Na⁺ and K⁺

Summary

• 1. Treatment of the isolated rectum ofPeriplaneta americana in vitro with extract prepared from the corpora cardiaca and corpora allata (1 pair combined glands ml⁻¹) increases oxygen uptake by 37%. The response is concentration dependent and appears to be specific to the rectum.

• 2. If Na⁺ in the Ringer solution is replaced with isomolar choline the respiration of control tissues is reduced 34%. The level of respiration is not increased by cardiaca-allata extract when Na⁺ is absent. Ouabain added to the Ringer solution has an effect similar to the omission of Na⁺. The gland extract partially overcomes the effect of ouabain.

• 3. Replacement of K⁺ with choline in the Ringer solution causes an 18% rise in the basal respiration. The absence of K⁺ does not interfere with the increase in respiration caused by the gland extract.

• 4. Treatment of the rectum in vitro with 1 mM dibutyryl cyclic 3′,5′-AMP increases respiration by 10%.

• 5. Treatment of the isolated rectum in vitro with gland extract (1 pair ml⁻¹) increases phosphorylase activity by at least 60%. This effect is completely blocked if Na⁺ is replaced with choline in the Ringer solution or 2 mM ouabain added.

• 6. Experiments with open and ligated recta indicate that receptors for the active factor are located on the surface of the rectum facing the haemolymph. The data suggest that the factor may accelerate the rate of Na⁺ transport by making the interior of the cell more accessible to Na⁺ in the bathing medium.