AN INHIBITOR OF DIACYLGLYCEROL-ACTIVATED PROTEIN-KINASE CS BLOCKS THEEFFECTS OF A DIACYLGLYCEROL LIPASE INHIBITOR, U-57908, ON THE LIGHT-DEPENDENT RENEWAL OF CRAB RHABDOMS IN-VITRO

1. We have previously shown that the regrowth of R1-6 rhabdoms of a cr ab, Leptograpsus, in darkness after brief illumination is enhanced by an inhibitor of diacylglycerol lipases, U-57908 2. We now show that th e effects of U-57908 are blocked by a specific inhibitor of diacylglyc erol activation of protein kinase Cs, AMG-C-16. However, AMG-C-16 alon e has no effect when results are compared to Controls in the absence o f either drug. 3. After 4 h in darkness, the sizes of R1-6 rhabdoms st art to increase, however retinas are treated with drugs. We presume th e existence of several regulatory pathways, one of which may relate to the endogenous circadian rhythms that our previous studies have impli ed. 4. We have previously demonstrated that perturbation of rhabdom re newal by drugs that affect the phosphorylation/dephosphorylation of pr oteins might implicate factors that regulate the transcription of rhab domeral membrane precursors. The relevant drugs provoke the differenti ation of photoreceptor nuclear envelopes to endoplasmic reticulum whic h appears to enter the pathway for rhabdomeral renewal demonstrated by Stowe (1980). AMG-C-16 blocks such nuclear envelope events. 5. Any sy stem that demands precise regulation of physiological events if it is to function effectively can be expected to rest upon several interlock ed regulatory pathways, as our cumulative results from crab retinas im ply.