# TRIIODTHYRONINE (T3) ENHANCES THE STIMULATORY EFFECT OF 1, 25-DIHYDROXYVITAMIN D3 ON CALBINDIN-D28k mRNA EXPRESSION IN THE KIDNEY AND INTESTINE BUT NOT IN CEREBELLUM OF THE CHICK

• Sechman, A. (Japan Society for Promotion of Science Postdoctoral fellow on leave from Department of Animal Physiology, Academy of Agriculture) ;
• Shimada, K. (Laboratory of Animal Physiology, School of Agricultural Sciences, Nagoya University) ;
• Saito, N. (Laboratory of Animal Physiology, School of Agricultural Sciences, Nagoya University) ;
• Ieda, T. (Laboratory of Animal Physiology, School of Agricultural Sciences, Nagoya University) ;
• Ono, T. (Faculty of Agriculture, Shinshu University)
• Accepted : 1995.08.11
• Published : 1996.02.01
• 88 5

#### Abstract

The present study was conducted to investigate the role of thyroid hormones in the regulation of gene expression of calbindin-$D_{28k}$ (CaBP-D28K) in the chicken. By employing slot blot and RIA analyses, levels of CABP-D28K mRNA and CaBP-D28K protein in the intestine, kidney, cerebellum and liver were measured 6 and 12 h after i.m. injection of 1, 25-dihydroxyvitamin $D_3$ [1, 25 $(OH)_2D_3$; 250 ng/chick] and 3, 5, 3'-triiodothyronine ($T_3$; 500 ng/chick) in one-day-old chicks. The abundant messages of CaBP-D28K mRNA were detected in the intestine, kidney and cerebellum while there was little message in the liver. After 1, 25 $(OH)_2D_3$ treatment (6 + 12 hours), levels of CaBP-D28K mRNA increased in the intestine, but there was no change in the mRNA levels in the kidney and cerebellum. Although $T_3$ alone had no effect on CaBP-D28K mRNA levels, simultaneous administration of $T_3$ enhanced the 1, 25 $(OH)_2D_3$ effect of levels of CaBP-D28K mRNA in the intestine both 6 and 12 h post-treatment, and in the kidney 12 h post-treatment. At a protein level, co-treatment with 1, 25 $(OH)_2D_3$ and $T_3$ elicited a significant increase in CaBP-D28K expression in the intestine 12 h post-treatment, as compared to treatment with only 1, 25 $(OH)_2D_3$, whereas no differences were observed in the CaBP-D28K protein levels in the kidney and cerebellum. These results suggest that thyroid hormones may play a synergistic role with 1, 25 $(OH)_2D_3$ for CaBP-D28K gene expression in the intestine and kidney in chicks.

#### Acknowledgement

Supported by : Ministry of Education of Japan