The present study aims to evaluate EGF contents by quantitative immunoelectron microscopy (QIEM) and radioimmunoassay (RIA), and also examined secretory granules (SG) in granular convoluted tubule (GCT) cells using a stereological method. QIEMEGF was demonstrated with the protein A-gold technique. Diameter of the SG was measured and QIME-EGF was determined, i.e. the number of gold particles/μm2 in the SG was calculated. Correlation between gold particles for EGF and sizes of SG was examined in GCT cells under administration of secretagogues; single injection of methoxamine to male mice, and 5 days injection with testosterone to females.
Histogram on the diameter of SGs generally a showed single peak. In normal male SMG, the size of SG (peak 1.2-1.5μm) was larger than in female SMG (peak 0.9-1.2μm), and many gold particles were found on the SG of GCT cells in normal males. The size of SG with positive EGF staining had a peak in 0.3-0.6μm at 12 hr after the single methoxamine injection. At 48 hr after administration of methoxamine and on the day after testosterone administration in female mice, sizes of SG showed the same peak as seen in the normal gland, however, QIME-EGF as a number of the gold particles/μm2 had not yet attained the control level. EGF concentration (RIA) in the submandibular gland (ng/mg wet weight) showed the same feature as QIME-EGF in the normal and treated mice.
The present results suggest that biosynthesis of EGF in GCT cells may be processed following recovery of the size of SG.
