Urine and kidney epidermal growth factor: ontogeny and sex difference in the mouse

We have explored the physiology of urinary epidermal growth factor (EGF) in the mouse by studying its ontogeny, and the effects of testosterone therapy on immunoreactive EGF (IR-EGF) concentrations in urine, kidney, serum and submandibular gland (SMG). Urine IR-EGF (U-EGF) increased about 100-fold relative to urea concentration and about 1000-fold relative to urine volume from the 1st day of life to adulthood. Most of this increase occurred between days 6 and 18, which is the known period of steep rise in plasma thyroid hormone concentration in the mouse. A small F greater than M sex difference was present in the adult. This difference was opposite in direction to the large M greater than F sex difference in adult SMG-EGF concentration. On day 26 (age of appearance of morphological sex difference in SMG) the sex difference was not yet present in urine, although in SMG it was even larger than in the adult. Kidney EGF concentration was low relative to U-EGF: 1 ml of adult urine contained approximately as much IR-EGF as 100 pairs of adult kidneys. In the adult, but not on day 26, there was a sex difference in kidney EGF concentration parallel to the sex difference in urine: female levels were about 30% higher than male levels. Ten days of testosterone treatment of adult female mice evoked an increase in IR-EGF concentration which was 1.7-fold for serum and 5-fold for SMG. In contrast, this treatment did not increase kidney or urine IR-EGF concentrations although kidney weight increased 1.3-fold.(ABSTRACT TRUNCATED AT 250 WORDS)