Effects of endogenous galanin on the growth of regenerating rat adrenal gland as investigated by the metaphase-arrest and the PCNA-immunostaining techniques

We have investigated the effects of three subcutaneous injections of 2 nmol/100 g body weight of galanin and its receptor antagonist (galanin-A) [D-Thr 6,D-Trp 8,9,-15-ol]-galanin 1-15 on the proliferative activity of regenerating rat adrenal cortex. The metaphase-arrest and the proliferating-cell nuclear antigen (PCNA)-immunostaining techniques were used to estimate the number of M phase (metaphase index) and S phase cells (PCNA index), respectively. Galanin-A raised the metaphase index at both day 5 and day 8 of regeneration. Galanin was per se ineffective, but reversed the galanin-A effect at day 8. Neither galanin nor galanin-A changed PCNA index at day 5. Galanin evoked a moderate increase in PCNA index at day 8. Taken together, these findings indicate that endogenous galanin exerts a tonic maximal inhibitory effect on adrenal regeneration in the rat.