Fractionated radiotherapy of rat prostatic adenocarcinoma (Dunning R3327-PAP) in nonanesthetized animals

BACKGROUND

The dose-response effect of fractionated external beam radiotherapy on nonanesthetized rats bearing the androgen-sensitive prostatic adenocarcinoma Dunning R3327-PAP was studied.

METHODS

The radiation was given with a photon beam from a 4-MeV linear accelerator in doses from 4 to 11 Gray per fraction during 5 consecutive days. When the tumors with low and intermediate radiation doses relapsed into regrowth, the rats were castrated. Tumor volumes and rat weights were followed, and at the end of the study a morphometric analysis of the tumors was done.

RESULTS

Fractionated irradiation induced a dose-dependent delay in tumor growth in hormonally intact rats. Castration stopped the tumor regrowth, showing that some of the tumor cells were still hormone-sensitive. The study was facilitated by the nonanesthesia procedure.

CONCLUSIONS

The Dunning R3327-PAP hormone-sensitive rat tumor is sensitive to radiotherapy in a dose-dependent way. Regrowing, irradiated tumors contain hormone-sensitive cells. This work provided basic knowledge for further experimental studies of the effects of radiation on prostatic adenocarcinoma.

Early castration-induced upregulation of transforming growth factor beta1 and its receptors is associated with tumor cell apoptosis and a major decline in serum prostate-specific antigen in prostate cancer patients

BACKGROUND

The mechanism behind castration-induced apoptosis in prostate cells is unknown, but data from other species suggest that transforming growth factor beta1 (TGF-beta1) may be involved.

METHODS

By using quantitative RT-PCR and immunohistochemistry, expression of TGF-beta1 and its receptors type I and II (RI and RII) was studied in normal and tumor areas of core biopsies taken before and 2-11 days after castration therapy. The TGF-beta responses were related to changes in apoptotic index and to changes in serum prostate-specific antigen (PSA).

RESULTS

In normal prostate tissue, apoptosis was generally increased by castration, and apoptosis was accompanied by an increase in TGF-beta1 and RII mRNA levels (P < 0.05). In tumors, apoptosis was seen only in 44% of the cases and in these, but not in the others, TGF-beta1, RI, and RII mRNA levels were increased (P < 0.05). In the patients showing a prognostically favorable PSA response (nadir PSA <5 ng/ml), but not in the others, RI and RII mRNA levels were significantly upregulated (P < 0.05).

CONCLUSIONS

Short-term upregulation of TGF-beta1 and its receptors is associated with apoptosis in human prostate and prostate cancer, and possibly with a favorable clinical outcome after castration therapy.

Predictive value of bcl-2 immunoreactivity in prostate cancer patients treated with radiotherapy

BACKGROUND AND PURPOSE

Recent experimental evidence suggests that overexpression of bcl-2, a protein functioning by blocking apoptosis, may influence the treatment outcome in human tumours, including prostate cancer. To test the clinical implications of this hypothesis, tumours from patients with prostate cancer treated with external beam radiotherapy were investigated for bcl-2 immunoreactivity (IR) and correlated with prognosis and treatment outcome.

MATERIALS AND METHODS

Bcl-2 IR was evaluated in archival tumour specimens obtained through transurethral resection from 42 patients with localized prostate cancer (T0-T4, N0 and M0). Bcl-2 IR expression was related to stage, grade and cancer-specific survival. Specimens were obtained prior to administrating routine radiotherapy for all patients.

RESULTS

Bcl-2 IR was present in 19/42 (45%) tumours. The bcl-2-positive patients had a significantly longer cancer-specific survival than the bcl-2-negative patients (10.3 versus 3.4 years, P<0.04). At follow-up (7-19 years), nine patients were still alive, 26 patients had died of prostate cancer and seven patients had died of other causes.

CONCLUSIONS

This study indicates that pre-treatment bcl-2 overexpression is related to a favourable outcome in prostate cancer treated with radiotherapy. Low bcl-2 along with a high stage may be a predictor of poor prognosis and these patients might benefit from additional treatment.

Evidence for a prostate cancer susceptibility locus on the X chromosome

Over 200,000 new prostate cancer cases are diagnosed in the United States each year, accounting for more than 35% of all cancer cases affecting men, and resulting in 40,000 deaths annually. Attempts to characterize genes predisposing to prostate cancer have been hampered by a high phenocopy rate, the late age of onset of the disease and, in the absence of distinguishing clinical features, the inability to stratify patients into subgroups relative to suspected genetic locus heterogeneity. We previously performed a genome-wide search for hereditary prostate cancer (HPC) genes, finding evidence of a prostate cancer susceptibility locus on chromosome 1 (termed HPC1; ref. 2). Here we present evidence for the location of a second prostate cancer susceptibility gene, which by heterogeneity estimates accounts for approximately 16% of HPC cases. This HPC locus resides on the X chromosome (Xq27-28), a finding consistent with results of previous population-based studies suggesting an X-linked mode of HPC inheritance. Linkage to Xq27-28 was observed in a combined study population of 360 prostate cancer families collected at four independent sites in North America, Finland and Sweden. A maximum two-point lod score of 4.60 was observed at DXS1113, theta=0.26, in the combined data set. Parametric multipoint and non-parametric analyses provided results consistent with the two-point analysis. Significant evidence for genetic locus heterogeneity was observed, with similar estimates of the proportion of linked families in each separate family collection. Genetic mapping of the locus represents an important initial step in the identification of an X-linked gene implicated in the aetiology of HPC.

Non-ortho PCB levels in various fish species from the east and west coast of Sweden

Non-ortho (coplanar) PCBs 77, 126 and 169 were determined in a number of fish species from the Swedish coastal environment, using either supercritical fluid extraction (SFE) or the traditional liquid/liquid extraction followed by HPLC separation on porous graphitic carbon (PGC) column prior to GC/MS analysis. While PCB 77 showed the highest concentration level, the TEQ value for PCB 126 was dominant in virtually all the samples analysed. The toxic equivalents, however, indicated some differences in analytical data between 1990 and 1992/93 but these are not significant probably owing to the short period in between.

Transforming growth factor beta1 is associated with angiogenesis, metastasis, and poor clinical outcome in prostate cancer

BACKGROUND

Prostate tumors express high levels of transforming growth factor-beta1 (TGF-beta1) and seem to acquire resistance to its antiproliferative effects with tumor progression. Moreover, TGF-beta1 could be involved in tumor-promoting processes such as angiogenesis, cell migration, and immunosuppression.

METHODS

Immunoreactivity for TGF-beta1 and its receptors type I and type II (TGFbeta-RI and TGFbeta-RII), tumor vascular count, and cell proliferation were studied in 73 cases of prostate cancer, diagnosed between 1975-1983 and followed with surveillance.

RESULTS

Patients with tumor overproduction of TGF-beta1 had shorter median cancer-specific survival than patients with normal TGF-beta1 immunoreactivity (5.0 vs. 10 years, P = 0.006). Furthermore, increased TGF-beta1 staining was associated with tumor grade, high vascular counts, and metastasis (P = 0.02, 0.02, and 0.01, respectively). Patients with loss of tumor TGFbeta-RII expression in combination with TGF-beta1 overproduction showed particularly short survival (2.6 vs. 10 years, P = 0.0000), when compared to patients with normal immunoreactivity.

CONCLUSIONS

Overproduction of TGF-beta1 and loss of TGFbeta-RII expression are associated with poor clinical outcome in prostate cancer, and TGF-beta1 may promote tumor progression by stimulating angiogenesis and metastasis.

Apoptosis and other mechanisms in androgen ablation treatment and androgen independent progression of prostate cancer: a review

Patients with advanced prostate cancer commonly present with disseminated disease. For these patients, androgen ablation is a first-line treatment. This mode of therapy usually has an initially palliative effect on tumor-related symptoms and slows growth, although virtually all tumors eventually relapse to an androgen-independent, more aggressively growing phenotype. However, surprisingly little is known about the actions mediating the initial palliative effect as well as the initiation of androgen-independent tumor growth. In this review, some current concepts on mechanisms of androgen ablation treatment and androgen-independent progression of prostate cancer is highlighted. Special attention is given to the involvement of apoptosis in these processes.

Unilateral injection of neuropeptide Y decreases blood flow in the injected testis but may also increase blood flow in the contralateral testis

Neuropeptide Y (NPY) receptors have recently been described in intratesticular arterioles, but the role of NPY in testicular blood-flow regulation has not been examined. To explore this, we administered NPY in various doses (0.01-10 microg) via intratesticular injections and studied testicular microcirculation using a laser Doppler flow meter. NPY injection shows a dose-response pattern, with 1 microg (the most potent dose) causing a decrease (-42.4 +/- 3.7%, P < 0.00005) in blood flow in the ipsilateral testis of all the animals and an increase in blood flow in the contralateral testis (+17.2 +/- 5.6%, P = 0.03, n = 25 animals). The response in the contralateral testis was variable. A clear-cut increase was seen in 19 of the 25 animals examined, whereas either no response or a slight decrease was seen in the remaining six. The contralateral increase, which was not seen in the hindpaw on the same side, did not occur when the neuronal connections to the testes were blocked by injection of local anesthetics into the spermatic cord, either on the NPY-injected side or on the contralateral side. Our results suggest that NPY may serve as a vasoconstrictor in the testis, probably by acting on the NPY-Y1 receptors present on intratesticular arterioles. Local injection of NPY causes a major decrease in blood flow in the injected testis. This decrease is followed in the majority of animals studied by an increase in blood flow in the contralateral testis, an effect that seems to depend on neuronal mechanisms. This observation suggests that the testes may communicate under certain situations. The functional consequences of this remain to be elucidated.

Inhibitory effects of soy and rye diets on the development of Dunning R3327 prostate adenocarcinoma in rats

METHODS

Dunning R3327 PAP prostate tumors were transplanted in 125 rats, the rats were divided into five groups, and tumor development was examined for 24 weeks during treatment with diets containing 33% of soy flour (SD), rye bran (RB), heat-treated rye bran (HRB), or rye endosperm (RE).

RESULTS

In the SD, RB, and HRB groups, significantly fewer palpable tumors and lower tumor volume were detected 14 and 16 weeks after transplantation when compared with the control, fiber-free dietary (FF) group. The body weight was lower 16 weeks after tumor transplantation in the RB and HRB groups when compared with the control group (P < 0.05). Rats in the RB and the HRB groups had a significant lower energy intake than the FF group during the first metabolic observation period, 3-6 weeks after tumor transplantation (P < 0.05), whereas the energy intake was the same in all groups during the second metabolic observation period, 13-16 weeks after tumor transplantation. However, when the tumor volume was adjusted for the body weight of the animals, there were still significant lower tumor volumes in the SD, RB, and HRB groups compared with the FF group (P < 0.05). A significant increase in daily urinary excretion of the isoflavonoids, daidzein, O-desmethylangolensin, equol, and Genistein, was observed in the rats fed SD, and of the ligands enterolactone and enterodiol in the rats fed RB and HRB during both metabolic periods. There were no differences in testosterone levels between the groups.

CONCLUSIONS

The present study shows that SD inhibits implanted prostate cancer growth. Although RB and HRB had a protective effect, further studies are needed to exclude the possibility that a low energy intake played a role in this respect. The results suggest that phytoestrogens (isoflavonoids and ligands), may be responsible for the delayed prostate tumor growth.

Expression of vascular endothelial growth factor and its receptors in the rat ventral prostate and Dunning R3327 PAP adenocarcinoma before and after castration

BACKGROUND

Angiogenesis is important for prostate organogenesis and prostate cancer progression. It is not yet known whether androgens promote part of their control of prostate structure and function by influencing angiogenesis. The aim of this study was to explore the possible androgenic regulation of the angiogenic factor vascular endothelial growth factor (VEGF) and its receptors flt-1 and flk-1/KDR in the rat ventral prostate (VP) and Dunning R3327 PAP adenocarcinoma.

METHODS

RNA was prepared from VP and tumors of intact and castrated rats. VEGF, flt-1, and flk-1/KDR mRNA levels were determined using competitive RT-PCR.

RESULTS

VEGF121, VEGF165, and VEGF189 together with flt-1 and flk-1/KDR mRNA were detected. The VEGF, but not flt-1 mRNA levels were significantly decreased in the VP after castration. The Dunning tumor expressed high levels of mRNA for VEGF and its receptors compared to the VP. The flt-1 mRNA level in the tumor increased after castration, while the VEGF mRNA levels were unchanged.

CONCLUSIONS

Decreased mRNA expression of VEGF, but not flt-1, was found in the rat VP after castration. However, in the Dunning tumor, castration did not alter the expression of VEGF mRNA. Moreover, elevated levels of both mRNA for VEGF and its receptors relative to the VP were observed, indicating that the VEGF system may be important for Dunning tumor development.

[Gene for hereditary prostatic cancer has been located. New possibilities for early identification of men at risk]

Prostate cancer is currently the most common malignancy among men in Sweden, and an estimated 5-10 per cent of cases are hereditary. Several epidemiological studies have shown men whose close relatives are affected to be at 2-4-fold increased risk of developing prostate cancer. In a recent genetic linkage study of 91 Swedish and North American families with hereditary prostate cancer, the first susceptibility locus, HPC 1 (hereditary prostate cancer 1), was localised at positions 1q24-25 on the long arm of chromosome 1. In Sweden, we recommend men with a strong family history of prostate cancer to undergo annual prostate-specific antigen testing and digital rectal examination from the age of 50.

Short-term cellular effects induced by castration therapy in relation to clinical outcome in prostate cancer

To explore the relationship between short-term effects of castration therapy and clinical response, biopsies obtained before and a week after castration therapy from 15 responding and 13 non-responding patients with prostate cancer were investigated. The biopsies were assessed for regressive morphology, apoptotic index by morphological criteria, nuclear area, and immunoreactivity (IR) for Ki-67, p53, bcl-2, bax and Fas. The index was defined as the percentage of immunoreactive cells in a tumour. Regressive morphology was observed in 14 out of 15 responding tumours after therapy, compared with 4 out of 13 non-responders (P < 0.001). Median tumour epithelial cell nuclear area and Ki-67 index decreased equally in both groups. The median apoptotic index increased from 2.6 to 3.5 after castration among responders (P < 0.05), whereas it remained at 2.8 among non-responders. p53 IR was present in three tumours before castration; after therapy p53 reactivity was seen in three additional tumours belonging to the responding group. Median bcl-2 index increased in responders from 1.5 to 10.0 (P < 0.05), and in non-responders from 0.08 to 2.7 (P < 0.05). Bax IR and Fas IR were present in all tumours before therapy and unchanged after therapy. Thus, regressive morphology and an increase in apoptotic index were related to a favourable clinical response. These data suggest that it might be possible to predict the effect of castration therapy by examining tumour biopsies shortly after treatment.

Testosterone stimulates angiogenesis and vascular regrowth in the ventral prostate in castrated adult rats

The castration-induced regression and testosterone stimulated regrowth of the vasculature in the rat ventral prostate lobe were studied using stereological techniques. Seven days after castration, the endothelial cell proliferation rate (bromodeoxyuridine labeling index); the total weights of blood vessel walls, blood vessel lumina, endothelial cells, glandular epithelial cells; and total organ weight were all decreased. Within 2 days after sc treatment with testosterone, the total weights of blood vessel walls, endothelial cells, and vascular lumina, as well as the endothelial cell proliferation rate, were all normalized. In contrast to the rapid response of the vasculature, the total weight of glandular epithelium and total organ weight were not normalized during the 4 days of testosterone treatment. Growth of the vasculature apparently precedes growth of the glandular epithelium. The testosterone- dependent factors stimulating the vasculature are unknown, but factors derived from epithelial cells, mast cells (which accumulate in the prostate during the first day of testosterone treatment), and tissue macrophages could all be involved. Castration-induced regression and testosterone-stimulated regrowth of the prostatic vasculature can be used as an experimental model to study factors regulating angiogenesis and organ growth in the prostate.

Long-term outcome of conservative therapy in men presenting with voiding symptoms and prostate cancer

OBJECTIVE

To investigate the outcome of conservative therapy in men presenting with voiding symptoms and prostate cancer.

METHODS

A consecutive series of 186 men presenting with voiding symptoms and prostate cancer were treated with transurethral resection (TUR). Examination of the resected tissue revealed 70 nonpalpable prostate cancers and confirmed the clinical suspicion of prostate cancer in 116 palpable tumors; 47 tumors were well differentiated, 87 intermediate and 52 poorly differentiated. Bone scan indicated metastasis in 24 men, all asymptomatic. The men were followed and underwent orchidectomy if symptoms of generalized disease appeared.

RESULTS

After a follow-up of 13-21 years, 172/186 (92%) of the men had died, with 80/186 (43%) of the men dying of prostate cancer. The mean life expectancy was 6.3 years (confidence interval 5.4-7.1) compared with 10.2 years of an age-matched control group. In a subgroup of men with clinically localized disease, 26/97 (27%) died of prostate cancer. These men had a mean life expectancy of 7.1 years (confidence interval 6.0-8.3). Tumor stage and grade were highly significant predictors for cause-specific survival in uni- and multivariate analysis. Death from prostate cancer continued to occur beyond 10 years after diagnosis at a decreasing rate.

CONCLUSIONS

Patients with prostate cancer causing voiding symptoms at presentation severe enough to necessitate TUR had a less favorable outcome than asymptomatic patients with prostate cancer in previously reported series, even when stratified for stage and grade. It is suggested that voiding symptoms at diagnosis are a putative prognostic factor in prostate cancer.

Radioimmunoscintigraphy with a novel monoclonal antiprostate antibody (E4): an experimental study in nude mice

BACKGROUND

Prostate cancer is one of the leading causes of death among men, despite achievements in diagnosis and therapy. Radioimmunolocalization and radioimmunotherapy of malignant tumors have demonstrated increasing potential and may become useful tools in the management of prostate cancer.

METHODS

Nude mice were inoculated subcutaneously with cells from the poorly differentiated human prostate cancer cell line DU-145. The intact monoclonal antibody (MoAb) E4 and an intact anticytokeratin-8 MoAb, TS1, used for comparison were labeled with 125I and injected intraperitoneally (i.p.) in the mice. Repetitive quantitative scintigraphic recordings were performed during 1 month. The mice were killed at Day 29 after injection of the radiolabeled MoAb. The tumors and the organs were dissected and weighed. The remaining activity was measured in a gamma well counter. One part of the tumor was immediately fixed in Bouin's solution for autoradiography and the other in formaldehyde for microscopy.

RESULTS

The study demonstrated significant radioimmunolocalization of the MoAb E4 into the DU-145 prostate tumor tissue in the animal model, with an average radiation dose of 0.08 Gy/MBq in the tumor. TS1 localized preferentially in necrotic parts of the tumor, yielding a tumor dose of 0.02 Gy/MBq.

CONCLUSIONS

The MoAb E4 is a promising radiotracer for prostate cancer and may be used in radioimmunotherapy. As in earlier studies, TS1 shows significant radioimmunolocalization into necrotic tumor tissue, which also exists in prostate cancer.

Effects of vasoactive intestinal peptide (VIP) on the testicular vasculature of the rat

Using laser Doppler flowmetry, the effects of unilateral intratesticular injection of vasoactive intestinal peptide (VIP) on testicular blood flow and mean arterial blood pressure were studied in anaesthetized adult rats. At doses of 50 and 500 ng, VIP increased blood flow by 29 +/- 8 and by 77 +/- 25% (p < 0.05), respectively (means +/- SEM) at 5 mm, but not at 15 mm, from the injection site. Blood pressure was not significantly affected by 50 ng, but was slightly reduced (by -8 +/- 2%) after treatment with 500 ng VIP. The highest dose of VIP (5 micrograms) reduced blood pressure (by -30 +/- 9%), and decreased blood flow at 15 mm, but not at 5 mm, from the injection site. It is concluded that VIP can act as a vasodilator in the rat testis.

Combined castration and fractionated radiotherapy in an experimental prostatic adenocarcinoma

PURPOSE

The present study using the Dunning R3327-PAP rat prostatic adenocarcinoma model was designed to study the effect on tumor growth of castration prior to or after irradiation with 20-25 Gy as compared with either irradiation or castration alone.

METHODS AND MATERIALS

Rats were bilaterally orchidectomized. During the irradiation procedure the nonanesthetized animals were held in a metallic frame with a strong cotton net and they were observed by means of a video camera. The suboptimal irradiation dose was given once daily with a 4-MeV linear accelerator, 4-5 Gy/fraction, during 5 consecutive days. Tumor volumes and rat weights were followed. At the end point of the study the animals were sacrificed and the tumors were morphometrically analyzed.

RESULTS

The combination of irradiation and castration delayed tumor regrowth better than irradiation alone with the same suboptimal dose. Castration before irradiation delayed tumor regrowth more efficiently than castration after irradiation. However, castration alone delayed tumor regrowth even more effectively than suboptimal irradiation doses combined with castration.

CONCLUSIONS

In combination with suboptimal irradiation neoadjuvant androgen deprivation was more inhibitory to rat prostatic adenocarcinoma regrowth than adjuvant androgen deprivation. Irradiation with suboptimal doses combined with castration may cause an earlier relapse to androgen-independent tumor growth than castration alone.

Decrement of blood flow precedes the involution of the ventral prostate in the rat after castration

Blood flow to the rat ventral prostate (VP), dorsolateral prostate (DP), and Dunning R3327 prostatic tumors was measured at different times up to 7 days after castration, using the microsphere method. In the VP organ weight was decreased from day 3 onwards. Blood flow was, however, already significantly decreased from day 1. The reduced blood flow in VP in 1-3 and 7-day castrated animals could be reversed by testosterone treatment. Organ weight was slightly decreased but blood flow was unaffected by castration in DP. Castration left Dunning tumor volume and blood flow unaffected. Using immunohistochemistry, androgen receptors were observed in epithelial and stromal cells in VP, DP and Dunning tumors, but not in blood vessels. Castration is known to induce apoptosis in the VP, but not in the DP or in Dunning tumors. This suggests that a reduction in blood flow might be an important component for the castration-induced involution and apoptosis in prostatic tissue. The reason why castration reduces blood flow only in the VP, and not in the DP or Dunning tumor is unknown.

Early age at diagnosis in families providing evidence of linkage to the hereditary prostate cancer locus (HPC1) on chromosome 1

In a recent study of 91 families having at least three first degree relatives with prostate cancer, we reported the localization of a major susceptibility locus for prostate cancer (HPC1) to chromosome 1 [band q24; J. R. Smith et al., Science (Washington DC), 274: 1371-1373, 1996]. There was significant evidence for locus heterogeneity, with an estimate of 34% of the families being linked to this locus. In this report, we investigate the importance of age at diagnosis of prostate cancer and number of affected individuals within a family as variables in the linkage analysis of an expanded set of markers on 1q24. Under two different models for the prostate cancer locus, we find that the evidence for linkage to HPC1 is provided primarily by large (five or more members affected) families with an early average age at diagnosis. Specifically, for 40 North American families with an average age at diagnosis <65 years, the multipoint lod score is 3.96, whereas for 39 families with an older average age at diagnosis, this value is -0.84. Assuming heterogeneity, the proportion of families linked is 66% for the 14 families with the earliest average ages at diagnoses, but it decreases to 7% for the families with the latest ages at diagnoses. A similar age effect is observed in 12 Swedish pedigrees analyzed. To test the hypotheses generated by these analyses, we examined an additional group of 13 newly identified prostate cancer families. Overall, these families provided additional evidence for linkage to this region (nonparametric linkage Z = 1.91; P = 0.04 at marker D1S1660), contributed primarily by the families in this group with early age at diagnosis [nonparametric linkage Z = 2.50 (P = 0.01) at D1S422]. These results are consistent with the existence of a locus in this region that predisposes men to develop early-onset prostate cancer.

Vascular density is a predictor of cancer-specific survival in prostatic carcinoma

BACKGROUND

Microvessel density has been shown to give prognostic information in a variety of solid tumors, but its role in prostatic carcinoma needs further elucidation.

METHODS

Intratumoral density of von Willebrand factor-positive microvessels was assessed in 98 cases of prostatic carcinoma, diagnosed at transurethral resection of the prostate (TURP) between 1975-1983, using two methods: 1) volume density of microvessels and 2) vascular count in the 2-3 most vascularized fields.

RESULTS

Volume density and vascular counts were highly correlated. In Kaplan-Meyer analysis, mean cancer-specific survival time for patients with a vascular count < 135 was significantly longer than for patients with a vascular count > 135 (P = 0.0064). The same results applied to patients with WHO grade II tumors (P = 0.01). Excluding metastasis in a multivariate analysis, both tumor stage and vascular count had an independent predictive value for cancer-specific survival in patients with WHO grade II tumors.

CONCLUSIONS

Microvessel density may predict cancer-specific survival in prostatic carcinoma.

Localization and effects of calcitonin gene-related peptide in the testicular vasculature of the rat

Using laser Doppler flowmetry, the effects of unilateral intratesticular injection of calcitonin gene-related peptide (CGRP) and CGRP8-37, a CGRP-receptor antagonist, on right- and left-testicular blood flow and mean arterial pressure were studied on anesthetized adult rats. Calcitonin gene-related peptide in doses of 5 and 50 ng increased blood flow 37 +/- 11% (mean +/- SEM, P < 0.05) and 30 +/- 5% at 5 mm, but not 15 mm, away from the injection site, respectively. They did not influence mean arterial pressure nor blood flow in the contralateral testis. Five-hundred nanogram doses increased testicular blood flow in the injected testis at a point 15 mm away from the injection site (22 +/- 3%, P < 0.05) and caused a slight decrease in mean arterial pressure (-12 +/- 3%, P < 0.05). The highest dose, 5 micrograms, caused a large (-39 +/- 3%, P < 0.05) fall in mean arterial pressure within 1 minute after injection, and testicular blood flow was reduced in both the injected (-9 +/- 2%, P < 0.05, 15 mm away from injection site) and contralateral testis (-20 +/- 5%, P < 0.05). Pretreatment with 500 ng of the receptor antagonist, CGRP8-37, did not significantly attenuate the blood flow increasing affect of 50 ng CGRP, nor did 50 micrograms CGRP 8-37 (given alone) influence basal testicular blood flow in the injected testis. Using Immunohistochemistry, CGRP-containing nerves were observed in the superior and interior spermatic nerves, in the testicular artery, and in the veins leaving the testis but not in intratesticular blood vessels.

CONCLUSIONS

1) CGRP is a potent vasodilator in the testicular vasculature and it may be involved in the local regulation of testicular blood flow: 2) the testis has limited capacity to autoregulate and is consequently unable to maintain a constant testicular blood flow during large and rapid reductions in blood pressure, and 3) the local and systemic effects of vasodilators act in opposite directions in the testis.

Is nitric oxide involved in the regulation of the rat testicular vasculature?

Using immunohistochemistry, endothelial nitric oxide synthase (NOS), and neuronal NOS were localized in the endothelium of rat testicular arteries and in Leydig cells, respectively. NADPH-diaphorase activity, indicating NOS activity, however, was present only in endothelial cells. In order to examine the role of nitric oxide (NO) in the regulation of rat testicular vasculature, intact and hCG-pretreated (50-100 IU hCG given s.c. 6 h earlier) animals were given injections of the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), 10 mg/kg i.v.). In all rats this resulted in a major increase in blood pressure. In intact, unstimulated animals, testicular vascular resistance was unaffected, and testicular blood flow consequently increased. In hCG-treated animals, in contrast, vascular resistance increased in an hCG dose-related way. L-NAME treatment also increased the hCG-induced accumulation of polymorphonuclear leukocytes in testicular venules. Treatment with N(G)-nitro-D-arginine methyl ester (D-NAME, 10 mg/kg i.v.), an inactive isomer of L-NAME, had no effect on the testicular vasculature. The study suggests that NO plays only a limited role in the regulation of testicular blood flow under basal conditions. After hCG treatment, however, NOS activity appears to be increased (increased endothelial NADPH-diaphorase staining), suggesting that NO in this situation is of importance to increase blood flow and to inhibit leukocyte accumulation.

Soy and rye diets inhibit the development of Dunning R3327 prostatic adenocarcinoma in rats

Two experiments were conducted to investigate the effect of soy and rye on the development of Dunning R3327 prostatic adenocarcinoma in rats.

Atrial natriuretic peptide, brain natriuretic peptide and c-type natriuretic peptide: effects on testicular microcirculation and immunohistochemical localization

The effect of local injection of atrial (ANP), brain (BNP) and C-type (CNP) natriuretic peptides and an ANP antagonist (HS-142-1) on testicular microcirculation and vasomotion was studied using laser Doppler flowmetry. The natriuretic peptides were also localized immunohistochemically within the testis. ANP, BNP-32, CNP-22 and CNP-53 all caused a dose-related increase in testicular blood flow. The effect of ANP was blocked by concomitant injection of the ANP antagonist. Immunoreactive (ir) CNP and ir BNP were found in Leydig cells whereas in ANP was observed in the seminiferous tubules. It is suggested that the natriuretic peptides could play a role in local regulation of the testicular microcirculation.