THE DIURETIC ACTIVITY OF A SERIES OF CEPHALOMYOTROPIC NEUROPEPTIDES, THE ACHETAKININS, ON ISOLATED MALPIGHIAN TUBULES OF THE HOUSE CRICKET, ACHETA-DOMESTICUS

At 10-9 M achetakinins double the rate of fluid secretion by isolated Malpighian tubules of the house cricket, Acheta domesticus. They appear to act independently of cAMP, and the diuretic responses to a cAMP analogue (8-bromo-cAMP) and achetakinin-I are additive. At 10-9 M achetakinin-I potentiates the diuretic response to exogenous 8-bromo-cAMP. In the presence of 10-5 M 8-bromo-cAMP, achetakinins, I, II, III, IV and V stimulate fluid secretion maximally, and have ED50 values ranging from 1.8 × 10-11 M to 3.2× 10-10 M. The pentapeptide C-terminal sequence FX1X2WG. NH2 (where X1 = H, N, S, Y, and X2 = S or P), common to achetakinins I-V, is all that is required for full biological activity. A possible role for achetakinins as diuretic hormones in vivo is discussed. © 1990.