The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis an...

http://www.afboard.com/library/creatinemetabolism.pdf

Creatine and Creatinine Metabolism

Guanidinoacetate methyltransferase (GAMT) catalyzes the last step of the biosynthetic pathway to creatine (Cr), the transfer of a methyl group from S-adenosylmethionine to guanidinoacetate. Despite the importance of this methylation reaction in cellular energy metabolism and in methyl group metabolism, a systematic study of the expression and cellular localization of this enzyme is lacking. As a means for determining why the testis and seminal vesicles contain high levels of Cr, we analyzed GAMT protein and mRNA levels in mouse tissues by Western and Northern blot analyses. The results show that GAMT was regulated at tissuespecific levels; the enzyme was most highly expressed in testis, caput epididymis, ovary, and liver. Differences were also noted between sexes; the levels of GAMT mRNA and protein were higher in female liver than in male liver. Furthermore, as the male mouse developed from neonatal stages through sexual maturity, the GAMT protein level increased in testis but decreased in liver. Immunohistochemical labeling showed that GAMT was localized primarily in Sertoli cells of the testis and in microvilli of the epithelial cells lining the caput epididymis. GAMT expression in Sertoli cells was confirmed by biochemical and molecular analyses of purified testicular cells, testes from prepubertal mice of different ages, and germ cell-deficient mutant mouse testes. These results indicate that Cr is synthesized extensively in the epithelia of seminiferous tubules and caput epididymis, suggesting that GAMT or metabolic pathways related to Cr biosynthesis may be important for germ cell development or function.

Guanidinoacetate methyltransferase in the mouse: extensive expression in Sertoli cells of testis and in microvilli of caput epididymis.

A transrectal probe for 1H imaging and 31P MR spectroscopy of the prostate gland is described. The probe is covered with plastic and consists of an insectional portion containing an rf coil and a handle containing a tuning and matching circuit. Using this transrectal probe, 1H MR images and the first 31P MR spectra of the in situ canine prostate were obtained. Serial alterations in prostate size and changes in the ratio of phosphomonoesters to ATP ratio following orchiectomy were observed. Transrectal images of the prostate appear to be superior to conventional whole body coil images in the canine. For the first time a device to obtain high signal-to-noise 1H images and 31P spectra of the in situ prostate has been constructed. This will allow the assessment of transrectal imaging and spectroscopy as tools for medical studies of prostate pathophysiology.

Transrectal probe for 1H MRI and 31P MR spectroscopy of the prostate gland

A single dose of cadmium chloride (3.23 μmol Cd2+/kg) causing acute testicular damage in male rats also caused significant creatinuria and creatinaemia at 48 h after dosing. Doses of cadmium which did not cause testicular necrosis did not cause creatinuria or creatinaemia. Surgical ligation of the pampiniform plexus also caused ischaemic necrosis of the testis and this was followed by significant creatinuria and creatinaemia. However, neither orchidectomy followed by a toxic dose of cadmium, orchidectomy alone nor sham operation caused significant creatinuria or creatinaemia. Cadmium dosing induced a temporary loss of body weight which was less than that caused by food restriction. Food restriction did not cause significant creatinuria but did cause significant creatinaemia. These data suggest that the creatine is derived from the damaged testis and that measurement of urinary creatine may be a useful non-invasive means of detecting acute testicular damage caused by exposure to chemicals or mechanical impairment of blood flow.

Studies on the relationship between acute testicular damage and urinary and plasma creatine concentration.

A history of biological applications of NMR spectroscopy

Phorphorus NMR spectra of the whole reproductive organs of male rats and their perchloric acid extracts indicate the presence of phosphocholine and phosphoethanolamine in the testis, glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) in the epididymis, and creatine phosphate, GPC, and GPE in the seminal vesicles. High amounts of carnitine and inositol were observed by the proton NMR of perchloric acid extract of the corpus and cauda epididymis. Smaller amounts of these compounds were observed in the caput epididymis and vas deferens; they were totally absent in the testis. Creatine is present in high concentrations in the testis, vas deferens, and seminal vesicles. It is almost absent in all parts of the epididymis.

Phosphorus-31 and proton NMR analysis of reproductive organs of male rats.

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Phosphorus-31 and proton NMR analysis of reproductive organs of male rats.