Proteolytic Fragmentation of Rat Prolactin by the Rat Ventral Prostate Gland

Compton, Mark M.; Witorsch, Raphael J.

doi:10.1016/s0022-5347(17)51665-1

Cited by 2 publications

(2 citation statements)

References 8 publications

(9 reference statements)

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“…Based on a wide literature in experimental models, hyperprolactinemia should induce prostate hypertrophy (1-3, 5, 6). PRL is expressed in rat and human prostate epithelium (6,27), and thus the prostate, in analogy with other tissues, can directly process PRL by posttranslational glycosylation, phosphorylation, or proteolytic cleavage (28,29) into molecular derivatives, with different cellular targets and biological activities. The level of locally produced prostatic PRL was demonstrated to be regulated by androgens (30).…”

Section: Discussionmentioning

confidence: 99%

Prolactin and Prostate Hypertrophy: A Pilot Observational, Prospective, Case-Control Study in Men with Prolactinoma

Colao¹,

Vitale²,

Sarno³

et al. 2004

The Journal of Clinical Endocrinology & Metabolism

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In experimental models, prolactin (PRL) displays independent hypertrophic effects on the prostate. To investigate whether hyperprolactinemia is associated with prostate enlargement in humans, we designed this open, prospective, case-control study enrolling 20 men with prolactinoma (aged 34 +/- 10 yr) and 20 age-matched healthy men. The endocrine profile and prostate transrectal ultrasonography were performed before and after 12 and 24 months of cabergoline treatment in the patients and at study entry and after 24 months in the controls. The patients had lower serum testosterone, dihydrotestosterone (DHT), and IGF-I levels and prostate volume (15.4 +/- 3.5 vs. 19.6 +/- 5.1 ml; P < 0.001) and higher PRL levels and prostate-specific antigen density than controls. There was no difference in prostate and transitional zone volumes between patients with normoandrogenemia (n = 8) or hypoandrogenemia (n = 12). After 12 and 24 months of treatment, PRL, testosterone, and DHT levels were normal in all cases, as were IGF-I and IGF-binding protein-3 levels. After 24 months, prostate volume was comparable to that in controls (21.7 +/- 4.5 vs. 22.5 +/- 4.7 ml). There were no changes in prostate structure throughout the study period in either the patients or the controls. In conclusion, in young men with prolactinoma PRL excess is unlikely to have effects on the prostate per se, because it is accompanied by low testosterone and DHT levels that produce the major effects.

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Section: Discussionmentioning

confidence: 99%

Prolactin and Prostate Hypertrophy: A Pilot Observational, Prospective, Case-Control Study in Men with Prolactinoma

Colao¹,

Vitale²,

Sarno³

et al. 2004

The Journal of Clinical Endocrinology & Metabolism

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“…Recently, Witorsch and colleagues (12)(13)(14) showed that the prostate and mammary gland (MG) contain enzymes that can convert intact rPRL into the cleaved variant form and its 16K fragment. These results raised the interesting possibility that cleavage of the PRL molecule could be a normal function of its target tissues and that such processing could be of physiological significance.…”

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confidence: 99%

Analysis of the Proteolytic Cleavage of Prolactin by the Mammary Gland and Liver of the Rat: Characterization of the Cleaved and 16K Forms*

Clapp

1987

Endocrinology

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A cleaved form of PRL (CPRL) has been reported to exist naturally in the pituitary and to be the main product of PRL proteolysis by its target tissues. A 16K fragment derived from CPRL has mammary mitogenic activity. To analyze the possible functional significance of the cleavage of PRL generated by incubation of unlabeled rat (r) PRL with a 25,000 generated by incubation of unlabeled rat (r) PRL with a 25,000 x g pellet from the mammary gland and liver of rats. The optimum pH for cleavage was 3.4. PRL and the cleaved products were easily identified and separated from other proteins in the sample. The mammary gland pellet from lactating rats was significantly more potent at cleaving the rPRL molecule than were those of virgin or pregnant rats. However, the livers of all rats showed a similar PRL-cleaving potency. Thus, target tissues may differ in their PRL-cleaving potencies in different physiological states. The PRL-cleaving activity was also present in rat milk. While cleaved and 16K PRLs were the only proteolytic products obtained from rPRL, the PRLs (ovine and human) or the GHs (rat, bovine, and human) of other species were processed into a variety of low mol wt forms. Human placental lactogen was not modified. Accordingly, the processing of rPRL by target tissue enzymes appears to be hormone and species specific. Cleaved and 16K PRLs had 100% and 6.5% of the binding activity for rat liver PRL receptors as did intact rPRL, respectively. Nevertheless, the 16K form may still be of physiological significance.

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Proteolytic Fragmentation of Rat Prolactin by the Rat Ventral Prostate Gland

Cited by 2 publications

References 8 publications

Prolactin and Prostate Hypertrophy: A Pilot Observational, Prospective, Case-Control Study in Men with Prolactinoma

Prolactin and Prostate Hypertrophy: A Pilot Observational, Prospective, Case-Control Study in Men with Prolactinoma

Analysis of the Proteolytic Cleavage of Prolactin by the Mammary Gland and Liver of the Rat: Characterization of the Cleaved and 16K Forms*

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