Characterization of insulin receptors in isolated epithelial cells of rat ventral prostate: Effect of fasting

Abstract

Insulin receptors have been characterized in rat prostatic epithelial cells by using [125I]insulin and a variety of physicochemical conditions. The binding data at equilibrium (2 h at 15 degrees C) could be interpreted in terms of two populations of insulin receptors: a class of receptors with high affinity (Kd = 2.16 nM) and low binding capacity (28.0 fmol mg-1 protein), and another class of receptors with low affinity (Kd = 0.29 microM) and high binding capacity (1.43 pmol mg-1 protein). Proinsulin exhibited a 63-fold lower affinity than insulin for binding sites whereas unrelated peptides were ineffective. The specific binding of insulin increased by about 50 per cent after 96 h of fasting; this increase could be explained by an increase of both the number of the high affinity-low capacity sites and the affinity of the low affinity-high capacity sites. These results together with previous studies on insulin action at the prostatic level strongly suggest that insulin may exert a physiological role on the prostatic epithelium.

Serum insulin level, disease stage, prostate specific antigen (PSA) and Gleason score in prostate cancer

“…But there has been little investigation into the role insulin itself plays in prostate cancer. Isolated epithelial cells of rat ventral prostate have insulin receptors, and fasting increases their concentration (Carmena et al, 1986). But PA-III rat prostate adenocarcinoma cells have no insulin receptor, though they do have specific binding sites for IGF-I and II (Polychronakos et al, 1991).…”

Effect of Short—Term Starvation on Leydig Cell Function in Adult Rats

“…In our study LHhCG binding to Leydig cell was similar in fed and fasted rats, which also supports this hypothesis. The maintenance of normal insulin levels in interstitial fluid despite declining systemic insulin values in fasted rats is additional evidence that insulin levels found in the testis and especially in interstitial fluid are independent of plasma concentration [ 10, 181. Starvation has been associated with increased insulin binding to main targets [3] but also to the prostatic gland, which is not considered as a target tissue for insulin [9]. Leydig cells therefore appear to be an exception as regards to the starvation-related change of insulin receptors.…”

Somatostatin inhibits VIP‐ and isoproterenol‐stimulated cyclic AMP accumulation in rat prostatic epithelial cells

“…The present data together with previous results on the characterization of somatostatin-containing cells in the prostate gland [5,6] suggest a physiological involvement of the hormone acting in a local manner at this level. Furthermore, the increase of the number of hormones and neurotransmitters evoking a response from the cyclic AMP system [2][3][4] implies that the control of prostatic epithelial function may be exceedingly complex, involving not only androgens but also many other factors.…”

“…Previous studies from our laboratory have shown that the prostatic cyclic AMP system is activated by a variety of agonists including classical neurotransmitters such as /Yadrenergic agonists [2] as well as more complex agents such as the neuropeptide vasoactive intestinal peptide (VIP) [3]. In contrast, the regulatory role of hormones or other factors negatively coupled to adenylate cyclase has not been as extensively investigated since only muscarinic receptors are known to lead to negative responses in this gland [4].…”