Detection of bikunin mRNA in limited portions of rat brain

Tissue distribution of bikunin mRNA, which encodes a Kunitz-type serine pro tease inhibitor of the inter-alpha-inhibitor family (I alpha I), was studie d in rats and mice by the reverse-transcripsion polymerase chain reaction ( RT-PCR). We found that the liver as well as other tissues, such as the kidn ey, testis and adrenal gland, expressed bikunin mRNA. Although signals of b ikunin mRNA were faint in the whole brain of rats and mice, distinct signal s were found in limited portions of rat brain, such as the hippocampus, cer ebral cortex and pituitary, but undetectable in cerebellum, medulla oblonga ta, hypothalamus, striatum, midbrain and choroid plexus. In three distinct types of cells, such as neurons, astrocytes and meningeal cells, in primary cultures isolated from the cerebral cortex and meninges of 1-day-old newbo rn rats, only neurons positively expressed bikunin mRNA. These results sugg est that, in addition to peripheral tissues, neurons in the hippocampus and cerebral cortex produce bikunin, suggesting a potential role of bikunin/I alpha I family in these brain regions.