Testicular expression of taste receptor type 1 subunit 3 (T1R3), a sweet/umami taste receptor, has been implicated in spermatogenesis and steroidogenesis in mice. We explored the role of testicular T1R3 in porcine postnatal development using the Congjiang Xiang pig, a rare Chinese miniature pig breed. Based on testicular weights, morphology, and testosterone levels, four key developmental stages were identified in the pig at postnatal days 15–180 (prepuberty: 30 day; early puberty: 60 day; late puberty: 90 day; sexual maturity: 120 day). During development, testicular T1R3 exhibited stage-dependent and cell-specific expression patterns. In particular, T1R3 levels increased significantly from prepuberty to puberty (p < 0.05), and expression remained high until sexual maturity (p < 0.05), similar to results for phospholipase Cβ2 (PLCβ2). The strong expressions of T1R3/PLCβ2 were observed at the cytoplasm of elongating/elongated spermatids and Leydig cells. In the eight-stage cycle of the seminiferous epithelium in pigs, T1R3/PLCβ2 levels were higher in the spermatogenic epithelium at stages II–VI than at the other stages, and the strong expressions were detected in elongating/elongated spermatids and residual bodies. The message RNA (mRNA) levels of taste receptor type 1 subunit 1 (T1R1) in the testis showed a similar trend to levels of T1R3. These data indicate a possible role of T1R3 in the regulation of spermatid differentiation and Leydig cell function.
Modified Davidson's Fluid (mDF) is a good fixative for morphological and antigen preservation. However, recent studies have shown that 4% paraformaldehyde (PFA) can better preserve the actin structure in rodent testes. It remains controversial which of these fixatives is best for testicular tissue. This study investigated the effects of both mDF and 4% PFA on the morphology and antigen preservation of Xiang pig testes using hematoxylin-eosin (HE) staining and immunohistochemistry (IHC). The stronger testis penetration of mDF compared with that of 4% PFA was primarily manifested as testicular color change and decrease in tissue weight loss. Testes fixed with 4% PFA displayed a severe shrinkage of both the tubular and interstitial compartments and the seminiferous tubule area decreased by 12.02% compared with that in mDF-fixed tissues. In contrast, IHC results showed that 4% PFA fixation achieved better IHC-positive performance than mDF fixation for antigens specifically expressed in germ cells, Leydig cells and Sertoli cells. Due to this improved antigen preservation by 4% PFA fixation, the relative immunoreactions intensity significantly increased by 39.8%, 27.8%, and 76.4%, respectively, compared with that in mDF fixation. In summary, fixation of Xiang pig testes with mDF was suitable for HE staining, while fixation with 4% PFA was more suitable for IHC.
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