Localization of beta-endorphin in tetrahymena by confocal microscopy. Induction of the prolonged production of the hormone by hormonal imprinting.

The unicellular Tetrahymena has hormone receptors and hormones which are characteristic of higher vertebrates, as well as similar signal transduction pathways. In the present experiments, immunocytochemistry and confocal microscopy were used to study the presence and localization of beta-endorphin in Tetrahymena pyriformis GL. Endorphin (or endorphin-like material) was localized in the cortical structures, oral field, cilia and nuclear envelope. One-hour treatment with beta-endorphin ('hormonal imprinting') increased the presence of immunocytochemically demonstrable endorphin immediately and after 24 h, and was especially strong after 96 h of treatment. Simultaneous treatment with naloxone, an opioid antagonist, did not inhibit endorphin effect, but had an additive effect on endorphin production. Naloxone alone induced a very intensive accumulation of endorphin 96 h after treatment. The results support the possibility of a hormone production being induced by the imprinting procedure, but the imprinter-like effect of naloxone also points to the importance in this case of non-discriminatory receptors also being involved in the process. Copyright 1999 Academic Press.