Hinton B T, Howards S S
Biol Reprod. 1982 Dec;27(5):1181-9. doi: 10.1095/biolreprod27.5.1181.
The in vivo movement of [3H] 3-0-methyl-D-glucose ([3H] 30MG), [3H] L-glucose, [3H] inositol and [3H] alpha-aminoisobutyric acid ([3H] alpha AIB) into and across the rat testicular and epididymal epithelium was investigated. After systemic infusion of [3H] 30MG, both epididymal and testicular tissue concentrations of the isotope were approximately 50% lower than blood plasma levels, even 24 h after infusion. Similar results were observed for caput and seminiferous tubule fluid. There was a significant reduction of [3H] 30MG caput lumen to blood ratio when the blood glucose concentration was increased to 2-5 times that of normal. A similar reduction of [3H] 30MG caput lumen to blood ratio was observed when 1000 mumol of 2-methylaminoisobutyric acid (meAIB) was infused with the isotope. Caput luminal [3H] L-glucose concentration never exceeded 10% of blood levels. The data suggest that glucose is transported across the testicular and epididymal epithelium via a facilitated diffusion mechanism (carrier mediated) and that the carrier is situated on the basolateral membrane. This study did not demonstrate either a glucose countertransport system or a glucose-inositol exchange system across the epithelium of the caput epididymidis. Epididymal tissue (except cauda) and caput luminal fluid concentrations of [3H] inositol exceeded that of blood plasma within 1 h after infusion of isotope. The proximal regions of the epididymis demonstrated significantly higher transporting activity than either cauda or testis. Systemic infusion of 100 mumol myo-inositol significantly reduced the transport of [3H] inositol into caput luminal fluid and epididymal and testicular tissue. It is suggested that there is a carrier situated on the basolateral membrane which is able to transport inositol against a concentration gradient (probably active transport). Epididymal tissue (except cauda), testicular tissue and caput luminal fluid concentrations of [3H] alpha AIB also exceeded that of blood plasma but only 24 h after infusion of isotope. The initial segment and corpus regions of the epididymis had a significantly higher transporting activity compared to the remainder of the epididymis and the testis. A dose of 500 mumol meAIB reduced epididymal uptake of [3H] alpha AIB. These results suggest that there is a carrier situated in the basolateral membrane which can transport the amino acid against a concentration gradient (probably active transport). The differences in transport activities of the compounds investigated along the reproductive tract probably indicate differences in the affinity or quantity of the carriers. These epididymal transporting systems regulate the movement of material across its epithelium and may help to protect the epididymis from fluctuations in the blood concentration of each compound.
研究了[³H] 3 - O - 甲基 - D - 葡萄糖（[³H] 30MG）、[³H] L - 葡萄糖、[³H] 肌醇和[³H] α - 氨基异丁酸（[³H] αAIB）在大鼠睾丸和附睾上皮内的体内移动及跨上皮移动情况。经系统输注[³H] 30MG后，即使在输注24小时后，附睾和睾丸组织中的同位素浓度仍比血浆水平低约50%。附睾头和生精小管液也观察到类似结果。当血糖浓度升高至正常的2 - 5倍时，[³H] 30MG附睾头管腔与血液的比值显著降低。当与同位素一起输注1000 μmol的2 - 甲基氨基异丁酸（meAIB）时，也观察到[³H] 30MG附睾头管腔与血液比值有类似降低。附睾头管腔中[³H] L - 葡萄糖浓度从未超过血液水平的10%。数据表明，葡萄糖通过易化扩散机制（载体介导）跨睾丸和附睾上皮运输，且载体位于基底外侧膜上。本研究未证明存在跨附睾头上皮的葡萄糖逆向转运系统或葡萄糖 - 肌醇交换系统。输注同位素后1小时内，附睾组织（尾段除外）和附睾头管腔液中[³H] 肌醇浓度超过血浆浓度。附睾近端区域的转运活性明显高于尾段或睾丸。系统输注100 μmol肌醇显著降低了[³H] 肌醇向附睾头管腔液以及附睾和睾丸组织中的转运。提示在基底外侧膜上存在一种载体，它能够逆浓度梯度转运肌醇（可能是主动转运）。附睾组织（尾段除外）、睾丸组织和附睾头管腔液中[³H] αAIB浓度也超过血浆浓度，但仅在输注同位素24小时后。附睾起始段和体部区域的转运活性明显高于附睾其余部分和睾丸。500 μmol meAIB剂量降低了附睾对[³H] αAIB的摄取。这些结果表明在基底外侧膜上存在一种载体，它能够逆浓度梯度转运氨基酸（可能是主动转运）。所研究化合物沿生殖道转运活性的差异可能表明载体亲和力或数量的差异。这些附睾转运系统调节物质跨其上皮的移动，并可能有助于保护附睾免受每种化合物血液浓度波动的影响。
