The present work studied the effects of epidermal growth factor (EGF) on the secretion of thyrotropin (TSH) from perifused pituitaries of 200 g body weight male Wistar rats. After decapitation the neural lobe was discarded and the anterior pituitary was transferred to a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199) through a reservoir to a chamber at a flow rate of 100 microliters/min. Individual chambers were filled with 600 microliters of medium and placed in a water bath at 37 degrees C. One ml samples of effluent were collected every 10 min for 60 min to obtain baseline values of TSH. Thereafter, TSH-releasing hormone (TRH) (10(-8) M) or EGF in varied concentrations (10(-8) M to 10(-11) M) were added to individual chambers. The 10 min sampling of effluent was then continued for 60 min to measure TSH by RIA (NIADDK, rTSH RP-2 standard). In the TRH study, the mean basal TSH concentration was 32.1 +/- 6.5 ng/ml, increasing to 105 +/- 13.8 ng at 10 min post-TRH (P less than 0.005) and declining to basal values at 20 min. Addition of EGF 10(-8) M increased TSH secretion from a mean basal value of 68.9 +/- 5.6 ng/ml to 201 +/- 44.3 ng/ml (P less than 0.02) and a return to normal value at 20 min. Similar effects were induced by EGF 10(-9) M (P less than 0.001) and 10(-10) M (P less than 0.05) whereas no effect was elicited by EGF 10(-11) M.(ABSTRACT TRUNCATED AT 250 WORDS)