Studies were undertaken to examine the effects of an
estradiol-chemical delivery system (E2-CDS) or
castration (CAST) on plasma
testosterone (T) and growth of the Segaloff 11095
carcinoma. Fischer 344 rats were implanted subcutaneously with the Segaloff 11095
tumor and
tumor growth was monitored thereafter. After optimal
tumor growth, when the average
tumor size was approximately 25 x 15 mm (length x width; 4-5 g wet weight), rats were randomized into (1) testis-intact controls; (2) CAST; (3) intact+E2-CDS groups (rats received weekly injection of the E2-CDS at 0.5 mg/kg). Animals were killed 7 or 14 days after the initiation of treatments. Blood and tissue samples were collected for subsequent analysis. Plasma T levels were suppressed by 98% and 97% through 14 days after CAST or
E2-CDS treatment. CAST increased plasma
gonadotropin (LH) concentrations, while
E2-CDS reduced LH compared to intact control levels.
E2-CDS treatment increased plasma E2 levels to 24 (one injection) or 75 pg/ml (two
injections) at 7 or 14 days, respectively.
E2-CDS, given once a week for 2 consecutive weeks, resulted in a decreased growth of the prostate
tumor by 61%, while CAST reduced the weights of these
tumors by only 20%. In response to
E2-CDS (one or two
injections), weights of the in situ ventral prostate and seminal vesicles were significantly reduced by 70% and 50%, respectively, in
tumor-bearing rats. Similarly, CAST reduced the weights of these tissues by 80% (prostate) or 52% (seminal vesicle) at 7 or 14 days
after treatment. Pituitary weight increased, while testes weight decreased by 20% with two
injections of
E2-CDS, compared with intact control rats. Collectively, these data indicate that
E2-CDS is effective in reducing the growth rate of prostatic
tumors in the rat.