Differences in regulation of testis specific lactate dehydrogenase in rat and mouse occur at multiple levels

The testis specific form of lactate dehydrogenase (LDH‐C₄) is encoded by a single locus, Ldh‐c, and is tightly regulated in a tissue specific manner. Here we show differences in expression of Ldh‐c between rat and mouse, and describe the levels at which regulation of this gene differs in the two species. Our results demonstrate that the Ldh‐c message level is nearly nine fold greater in mouse testis and remains high post‐meiotically. In contrast, rat Ldh‐c mRNA is highest in primary spermatocytes and reduced in spermatids. The results of nuclear run‐on assays indicate that the transcription rate of Ldh‐c is only moderately higher in mouse than rat, and cannot account for a significant portion of the observed differences. Similar decay rates for both rat and mouse Ldh‐c mRNA in actinomycin‐D clearance assays indicate comparable cytoplasmic stabilities for the two messages. From these results we infer that nuclear prostranscriptional events contribute to the differences in Ldh‐c message levels. © 1993 Wiley‐Liss, Inc.