Effect of Suckling on Serum Insulin-like Growth Factor- I Levels in the Primiparous Rat

Rat 의 포유조절이 혈중 Insulin-like Growth Factor- I 수준에 미치는 영향

This experiment was conducted to investigate how restricted-lactation and regulation of weaning-time influence the levels of insulin-like growth factor-I (IGF-I) in primiparous rats during the suckling period. All the rats were raised in the individual cage from a few days before parturition through the whole suckling period. The restrictedlactation (RL) and weaned (W) groups were subdivided into 5 subgroups as RL0, RL5, RL10, RL15 and RL20 as well as W0, W5, Wl0, W15, and W20 according to the day of onset of suckling only 4 pups in restriction lactation and of suckling no pups in weaned group, respectively, in contrast to suckling 8 pups per litter in normal lactation (NL) group. The results obtained were summarized as follows: 1. The serum IGF- I concentration of NL rats was 750.59$\pm$3.52ng/$m\ell$ on Day 0, which was not changed until Day 15, and then it was increased through the subsequent suckling period to 1690.20$\pm$4.42ng/$m\ell$ on Day 25. 2. The IGF-I concentrations of early restricted lactation (RL0, RL5) were 1395.90$\pm$3.45ng/$m\ell$ and 1351$\pm$3.23ng/$m\ell$ on Day 10, respeotively. It was significantly higher (P＜0.05) than NL group (745.96$\pm$2.24ng/$m\ell$), and then was not different between group from day 15 of lactation. 3. The IGF- I concentration of W-group in the early lactation was higher (P＜0.05) than NL group during the first week of lactation. But it was decreased to the similar concentration as NL group on Day 10. These data show that lactation stimulus may regulate the IGF-I concentration.

본 연구는 Wistar계 rat를 이용하여 포유기간 중 제한포유시기와 이유시기를 조절하여, 혈중 IGF- I 수준변화에 대해 검토하였다. NL군 (NL)은 포유자의 수를 8 마리로 조절하였으며, RL군 (RL)과 W군 (W)은 RL0, RL0, RL10, RLl5 및 RL20, 그리고 W0, W5, WI0, W15 및 W20으로 각각 5개 군으로 구분하여, RL군은 각 개시일에 포유자의 수를 8마리에서 4마리로 조절하였으며, W군은 각 개시일에 포유자의 수를 완전히 이유시켜 다음과 같은 결과를 얻었다. 1. NL군의 혈중 IGF-I 농도는 분만직후 (Day 0) 750.59$\pm$3.52ng/$m\ell$ 을 나타내어 15일까지 일정한 수준을 유지하다가 그 후 포유 25일에 1,690.20$\pm$4.42ng/$m\ell$ 까지 증가되었다. 2. 포유초기 RL군 (RL0, RL5)의 IGF- I 농도는 포유 10일에 RL0군과 RL5군에서 각각 1,395.90$\pm$3.45 및 1,351.73$\pm$3.23ng/$m\ell$로서 NL 군의 745.96$\pm$2.24ng/$m\ell$ 보다 유의적 (P＜0.05)으로 높게 나타났으나 포유 15일부터는 차이가 없었다. 3. 포유초기 W군의 IGF- I 농도는 이유 후 일주일 정도는 NL군에 비해 높은 수준 (P＜0.05)을 나타내다가 10일경에 NL군과 같은 수준으로 감소하였다. 포유자극의 강약은 난소의 생리적 변화와 함께 혈중 IGF- I의 농도를 조절하는 것으로 사료된다.