Neurohormonal control of ecdysteroid biosynthesis by Carcinus maenas Y-organs in vitro, and preliminary characterization of the putative molt-inhibiting hormone (MIH)

Abstract

Using simple culture techniques, the effects of neurosecretory tissue, sinus gland-conditioned media, and sinus gland extracts upon the biosynthesis of ecdysteroids by Carcinus maenas Y-organs in vitro were investigated. The sinus glands were found to be a major source of a factor which profoundly repressed ecdysteroid synthesis and which did not appear to be species-specific within other brachyurans examined ( Liocarcinus, Cancer). It is suggested that the inhibitory factor is produced by the neurosecretory tissues of the medulla terminalis. It is argued that the inhibitory factor is the the putative molt-inhibiting hormone (MIH). Partial characterization revealed that MIH is a heat-stable, trypsin-sensitive neuropeptide, eluting on a Sephadex G-50 gel in a range of approximately 6–14 kDa. By consideration of the dose-response characteristics, it is estimated that MIH may be active in the subpicomolar range.