Relationship between epidermal growth factor and its receptor in human benign prostatic hyperplasia.

Human benign prostatic hyperplasia (BPH) samples were analyzed to evaluate the presence of immunoreactive epidermal growth factor (irEGF) and EGF receptor (EGFR). In all BPH samples examined both peptide and its receptor were present. Scatchard analysis of binding data of [125I]EGF showed two classes of binding sites with high and low affinity. Intratissular irEGF concentrations showed a significant inverse linear correlation with EGFR levels. Two groups of samples can be identified: the first showing high irEGF concentrations and low levels of EGF binding sites; the second low irEGF and high concentrations of EGFR. The simultaneous presence of EGF and its receptor in BPH samples indicates that this growth factor may act in an autocrine/paracrine manner in human prostatic tissue. The inverse relationship between EGF and the two sites of EGFR lead one to hypothesize that EGF itself could play a central role in determining receptor cell surface availability.

Immunoreactive EGF in human benign prostatic hyperplasia: relationships with androgen and estrogen receptors.

Benign prostatic hyperplasia (BPH) is a sex steroid dependent disease. Estrogens and androgens can modulate in different mammalian tissues epidermal growth factor (EGF) production and/or secretion. In order to clarify the relationships between estrogen and androgen receptor concentrations and those of immunoreactive EGF (irEGF), we have evaluated these parameters in 14 human BPH samples, by means of a dextran-coated charcoal method and radioimmunoassay, respectively. Cytosolic steroid receptors did not seem to correlate with irEGF. A linear significative relationship was evident between nuclear androgen receptor (ARn) levels and endogenous irEGF but not between nuclear estrogen receptors and irEGF: in ARn negative BPH samples, irEGF levels were lower than in ARn positive ones. Therefore, it is possible that androgens act at prostatic tissue level, through their own receptors, by modulating EGF production and/or secretion.

Epidermal growth factor binding and steroid receptor content in human benign prostatic hyperplasia.

The receptor for epidermal growth factor (EGF-R) was characterized on membrane fractions from human benign prostatic hyperplasia (BPH). Specific binding of [125I]EGF reached equilibrium after 40 min at 25 degrees C and was stable for up to 120 min. Saturation analysis of EGF-R, performed by incubating the membranes with 0.0156-15 nM [125I]EGF in the presence and in the absence of 100-fold excess of cold EGF for 60 min, revealed the presence of two classes of binding sites with high and low affinities (Kd = 0.35 +/- 0.23 and 9.60 +/- 2.87 nM respectively). Competition experiments revealed that FSH, insulin and calcitonin did not compete with [125I]EGF. The simultaneous determination of EGF-R and that of estradiol (ER), progesterone (PR) and androgen receptors (AR) was performed using the same buffer to homogenate the tissues and to obtain cellular membranes. The steroid receptors (SR) were determined by means of the dextran-coated charcoal method. There was a significant negative correlation between nuclear SR and binding capacity of EGF-R. The presence of specific and high affinity binding sites for EGF and the modulation of the level of these sites by steroid receptors suggest a possible role of EGF in prostatic hyperplasia.