Springer Online Journal Archives 1860-2000
Summary The sequence of changes in RNA synthesis during the early phases of genesis of medullary bone induced in male Japanese quail by estrogen treatment was studied by 3H-uridine uptake. Analyses of plasma estrogen and testosterone were done by radioimmunoassay at 12, 24, 38 and 61 h. A dose of 5 mg kg-1 estradiol-17β was found to stimulate the same 3H-uridine uptake 15 h after hormone treatment as a dose of 20 mg kg-1 of estradiol valerate. The uptake of 3H-uridine rose as the dose of estradiol-17β increased. Plasma estrogen levels, which were highest 12 h after injection, declined sharply during the next 12 h, returning to control levels between 38 and 61 h. Testosterone levels declined after estrogen administration and remained below control values at all time points. Following estrogen administration, 3H-uridine uptake declined from control values for the first 8 h. Twelve hours after hormone administration control levels were again reached, with maximum 3H-uridine uptake occurring 16 h after hormone treatment. The 16-h maximum was followed by a steady decline to below control levels at 20, 24 and 28 h, the time at which the experiment was discontinued. Maximum 3H-uridine up-take following estrogen stimulation is similar to that observed for the stimulated immature rat uterus.
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