Relationship between receptors for epidermal growth factor and steroid hormones in normal, dysplastic and neoplastic canine mammary tissues.

The concentrations of receptors for epidermal growth factor (EGF-R), oestrogen (ER) and progesterone (PR) were measured in 108 samples from canine mammary tumours and 132 samples of normal mammary tissue removed surgically from 84 bitches. The history and clinical signs were also recorded. Binding sites of high affinity were detected in 70 per cent of both types of tissue and no significant variations in EGF-R concentrations or positivity were observed with the histology, location, size or number of mammary tumours or the age of the animal. A significant direct correlation (P = 0.002) was observed between the concentrations of ER and EGF-R only in malignant tumours. The concentrations of EGF-R were significantly correlated (P = 0.04) in normal mammary tissues adjacent to and distant from the lesions, but not between normal tissue and tumour tissue. No significant differences were observed in the expression of EGF-R in normal and neoplastic tissues from the same bitches. The direct correlation between the concentrations of EGF-R and ER in malignant tumours could be related to an oestrogen-dependent expression of EGF-R or to a similar pattern of regulation of the receptors.

Comparison of estrogen and progesterone receptor expression in normal and tumor mammary tissues from dogs.

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).(ABSTRACT TRUNCATED AT 250 WORDS)

Iodination of mouse EGF with chloramine T at 4 degrees C: characterization of the iodinated peptide and comparison with other labelling methods.

A modified Chloramine T labelling procedure was used to iodinate mEGF in order to perform radio-receptor assays. The reaction was conducted at 4 degrees C with 1 mu g Chloramine T only. The tracer obtained was characterized by its maximal binding, specific activity and binding properties compared with the native peptide. Fast Liquid Protein Chromatography was performed to analyse the homogeneity of the preparation and membrane extracts from A431 cells were used to purify the tracer. The modified Chloramine T procedure was compared with two other methods: the classical Chloramine T iodination and the labelling procedure using Enzymobeads. The modified Chloramine T procedure is reproducible, provides labelled mEGF with high binding capacity (65 to 80% with canine placental membrane extracts) and high specific activity (351 +/- 107 mu Ci/mu g mEGF) and seems to preserve the binding properties of the native peptide.

Changes in oestrogen, progesterone and epidermal growth factor receptor concentrations and affinities during the oestrous cycle in the normal mammary gland and uterus of dogs.

Changes in the concentrations and affinities of receptors for oestrogen (ER), progesterone (PR) and epidermal growth factor (EGF-R) were studied in mammary glands of healthy bitches with regard to age, the location in the mammary chain and the stage of the oestrous cycle. Uterus was used as the reference tissue for the evaluation of steroid receptors. Mammary and uterine samples from 7 healthy bitches were taken at five stages of the oestrous cycle in such a way that all the locations in the mammary chain were represented at each stage of the cycle (10 samples/dog). ER, PR and EGF-R were detected by biochemical assays using increasing concentrations of tritiated (steroids) or iodinated (EGF) ligands. A significant direct correlation was found between the ER and PR concentrations for mammary and uterine samples. No significant correlation was found between the steroid receptors and EGF-R concentrations. Mammary ER concentrations were significantly higher in bitches of 5 years of age or older than in younger ones; in posterior glands (4th and 5th pairs) than in anterior glands; and in the mid-luteal phase. Mammary PR did not vary significantly with age or location but was significantly lower in the early luteal phase than in other phases. A similar decrease in PR concentrations was observed in the uterus during the early luteal phase and uterine ER and PR concentrations were very low in the mid-luteal phase. Mammary EGF-R were not significantly higher in the early or mid-luteal phase than in pro-oestrus or anoestrus. The differences observed between the uterine and mammary steroid receptor concentrations during the oestrous cycle could be due to different mechanisms for regulating steroid receptor expression in the two tissues. Mammary EGF-R concentrations may be linked, as in other species, to cellular proliferation and/or to the serum progesterone concentrations.

Regulation of progesterone during pregnancy in the cat: studies on the roles of corpora lutea, placenta and prolactin secretion.

The regulation of progesterone secretion and release by the corpus luteum and/or by the placenta in cats during pregnancy has been poorly studied and the relative roles of the corpus luteum and the placenta in the release of progesterone into the plasma is not well defined. It is generally assumed that after 40-45 days of pregnancy, circulating progesterone is mainly produced by the placenta and that after 45-50 days the corpus luteum is no longer necessary to maintain pregnancy, even if remnants of corpora lutea are detected in the ovaries during the following interoestrous period. In this study, the relative roles of the placenta and ovary in progesterone production after 30 days of pregnancy have been analysed in an attempt to define the role of progesterone in pregnant cats. Different experiments involved (1) analysis of the effects of an ovariectomy performed at 30 days of pregnancy, and of megestrol acetate supplementation on plasma progesterone during the second half of pregnancy, (2) analysis of the effects of an ovariectomy performed at 45 days on plasma progesterone production and on pregnancy and (3) analysis of the effects of an antiprolactin agent (cabergoline) at days 30 and 40 of pregnancy on progesterone secretion and pregnancy. These results were all compared with the normal plasma progesterone profiles during (a) pseudopregnancy and (b) pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptors for oestrogen, progesterone and epidermal growth factor in normal and tumorous canine mammary tissues.

Receptors for oestrogen (ER), progesterone (PR) and epidermal growth factor (EGF-R) are found in normal mammary tissue (NMT) and/or mammary tumours (MT) from all species studied, including dogs. The aims of this study were to define the possible influences of mammary histology, age, location in the mammary chain and of hormonal status and cycle stage in the expression of ER, PR and EGF-R in mammary tissues from healthy dogs and from dogs with MT. Carcinomas that had lost their glandular structure had significantly lower amounts of receptors. NMT either from healthy or affected dogs had significantly higher amounts of ER than MT. PR levels were significantly higher in benign lesions than in NMT. Steroid receptors in NMT from healthy dogs varied significantly with age (older dogs having more ER), location (posterior glands having higher ER concentrations) and cycle stage (the highest ER concentrations being found in the mid-luteal phase and the lowest PR concentrations in the early luteal phase). In NMT from affected dogs, higher steroid receptor concentrations were found in posterior glands; as in healthy dogs, ER concentrations were low in the follicular phase and high in the luteal phase and PR were high in anoestrus. Steroid receptor content in MT did not vary significantly with age, location or cycle stage or with hormonal status, but tended to vary with cycle stage in a manner similar to that found in NMT from the same dogs. In dogs affected with MT and treated with medroxyprogesterone acetate (MPA), NMT had low concentrations of PR but MT from the same dogs had high PR concentrations. EGF-R were found in the majority of the samples (+/- 65% of MT and +/- 85% of NMT) but there was no significant relation between the concentrations and the parameters studied. Nevertheless, EGF-R content was higher in NMT in the proliferative stages (oestrus, early and mid-luteal phase) than in the non-proliferative stages (early pro-oestrus and anoestrus). EGF-R and ER were significantly and positively correlated only in malignant tumours. There is no apparent difference between affected and healthy dogs in the regulation of ER, PR and EGF-R expression in NMT; on the other hand, some differences between NMT and MT are observed in the regulation of PR (for example under the influence of MPA) and in the correlation between EGF-R and ER expression.