Epidermal growth factor in mouse urine: non-blood origin, and increase by sialoadenectomy and T4 therapy

To study the origin and regulation of urinary epidermal growth factor (U-EGF), we measured EGF in adult female mouse plasma, urine and kidney tissue. We also studied the effects of excision of the submandibular salivary gland (SMG) and, after SMG excision and sham operation, 10-day therapies with T4 (0.4 microgram/g daily), testosterone propionate (TP, 12.5 micrograms/g every 48 h), and SMG extract (25 micrograms EGF daily). We measured EGF with a specific liquid phase radioimmunoassay. The mean apparent urinary clearance was 150-fold higher for EGF than for urea. U-EGF was increased 24 h after the last sc injection of SMG extract. SMG excision caused a 2.2-fold increase in U-EGF and in apparent EGF clearance. T4 brought about a 1.5 to 1.75-fold increase in U-EGF while TP was without effect. Kidney EGF (K-EGF) responded to T4 and TP like U-EGF, but SMG excision and extract were without effect on K-EGF. We conclude that 1) the immunoassayable EGF in blood plasma and SMG-EGF do not appear to be major sources of U-EGF but plasma EGF may be a minor source, 2) kidney tissue appears not to be a major source of U-EGF, 3) production of U-EGF is activated by SMG excision, 4) T4 increases both U- and K-EGF while testosterone has no effect.