Concentrations of estrogen (ER) and progesterone (PR) receptors were measured by radioreceptor assay in tumor (n = 319) and normal (n = 166) mammary tissue from 248 bitches. Correlations between ER and PR and between receptor expression in tumor and normal mammary tissue from the same bitches were evaluated. The influence of tumor, clinical, or hormonal variables on receptor expression also was studied. Approximately 80% of tumor and 95% of normal mammary tissue expressed detectable concentrations of ER, PR, or both. Direct correlation was found between ER and PR concentrations in normal and tumor tissues. Median ER concentrations were significantly higher (46 +/- 47 fmol/mg of cytosolic protein vs 27 +/- 24 fmol/mg of cytosolic protein; P = 0.0002) in normal than in tumor tissue. On the other hand, PR concentrations were significantly higher (57 +/- 52 fmol/mg vs 77 +/- 99 fmol/mg; P = 0.03) in tumors (especially benign tumors) than in normal tissue. Poorly differentiated malignant tumors expressed lower concentrations of receptors than did benign or well differentiated malignant tumors. The ER and PR concentrations decreased with increasing size of the lesion. Hormonal status of the bitch significantly (P < 0.05) influenced receptor expression in normal tissue: bitches in the luteal phase of the estrous cycle had higher concentrations of ER (69 +/- 62 fmol/mg) than did ovariectomized bitches (24 +/- 19 fmol/mg) or bitches in anestrus (38 +/- 45 fmol/ mg) or the follicular phase (13 +/- 7 fmol/mg). For PR, higher concentrations were observed in normal tissue during anestrus than during pseudopregnancy or in bitches treated with medroxyprogesterone acetate. Similar, but nonsignificant, variations were seen in tumor tissue except in medroxyprogesterone acetate-treated bitches in which PR concentrations were high in tumors and low in normal tissue from the same bitches.

Effect of estrogen (E2) and progesterone (P4) on uterine antibacterial activity and immunoglobulin concentrations in mares was studied. In 2 in vitro experiments, 6 mixed-breed mares were ovariectomized, and uterine fluid and blood serum were analyzed. Antibacterial assay methods were used to determine inhibitory effects on Streptococcus zooepidemicus of uterine fluid samples collected on days 3, 5, and 8, and serum obtained on day 8 of treatment. Single radial immunodiffusion methods were used to quantify amounts of IgA and IgG in uterine fluid and serum on days 3, 5, 8, and 14 of treatment. Neither E2 nor P4 increased activity of serum and uterine fluid against S zooepidemicus. Numbers of colony-forming units per milliliter of bacteria were significantly (P < 0.01) lower in control Hanks' balanced salt solution with 1.0% gelatin (HBSSG) than in uterine fluids. Bacterial numbers were significantly (50%) greater in uterine fluids and serum than in HBSSG controls for both treatments. Both fluids, especially serum, supported significantly (P < 0.01) more growth of S zooepidemicus than did HBSSG when incubated for 0, 2, and 4 hours. These findings are in contrast to previous reports of antibacterial activity in the uterus of sexually intact mares undergoing an estrous cycle: great reduction of bacterial count in uterine fluid from mares in diestrus, and significant increases in bacterial numbers in uterine fluid or serum from mares in estrus. Treatment comparisons between serum and uterine fluid IgA and IgG concentrations were not significantly different, although overall IgA concentration in the uterus was higher than concentration in serum. The IgG concentration in uterine fluid was higher in P4- than E2-treated mares. However, IgG concentration was significantly (P < 0.01) higher in uterine fluid on day 8 in P4-treated mares than on day 3 or 5. Results of this study indicate that neither immunoglobulin concentration nor hormone treatment has a direct effec.