BASIC FIBROBLAST GROWTH-FACTOR RECEPTOR IN THE RAT ADRENAL-CORTEX - EFFECTS OF SURAMIN AND UNILATERAL ADRENALECTOMY ON RECEPTOR NUMBERS

Previous studies have suggested that basic fibroblast growth factor (b FGF) is involved in the mediation of the compensatory adrenal growth r esponse. These studies were undertaken to identify the bFGF receptor i n the rat adrenal cortex and determine bFGF receptor levels in vivo. I nitial studies using primary cultures of rat glomerulosa cells demonst rated a high affinity binding site with a K-d Of 10 pM, consistent wit h reported values for the bFGF receptor, however, these results could not be demonstrated in capsule-glomerulosa tissue. Using autoradiograp hy to verify the existence of bFGF receptors in. vivo, heparin-insensi tive [I-125]bFGF-binding sites were concentrated primarily in the caps ule and glomerulosa of the adrenal cortex, suggesting the presence of FGF receptors. The presence of bFGF receptors was further verified by demonstration of internalization of [(125)]bFGF into cells of capsule- glomerulosa preps. This approach was used to demonstrate that suramin (a bFGF antagonist) pretreatment of rots results in bFGF receptor up-r egulation in the adrenal cortex. In addition, we demonstrated a decrea se in bFGF internalization in the remaining adrenal 24 h after unilate ral adrenalectomy, suggesting the utilization of bFGF during the compe nsatory adrenal growth response. Together, these data support a role f or bFGF in autocrine stimulation of the adrenal cortex and in the comp ensatory adrenal growth response.