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Mouse gamma-renin is a member of the group of serine proteases known as glandular kallikreins. These highly homologous proteins process a diverse range of growth factors and hormones to their biologically active form, usually by cleavage at a basic residue. gamma-Renin, however, cleaves at a Leu-Leu bond in a similar fashion to renin. We have identified and sequenced the gene and a cDNA encoding gamma-renin. The complete predicted amino acid sequence was determined, and residues that may be important in the unusual cleavage pattern exhibited by gamma-renin are discussed. The nucleotide sequence enabled design of a gene-specific oligodeoxyribonucleotide which was used to determine in which mouse tissues gamma-renin is expressed.

1. We have developed a method for non-invasive measurement of lung tissue mass, thoracic blood and interstitial volumes by a combination of transmission and emission scanning with technetium isotope (99mTc). 2. In a lung model we demonstrated that emission counts could be successfully corrected for attenuation with data obtained by transmission scanning, despite an uneven distribution of radioactivity and attenuation in the model. 3. In dogs we compared regional transthoracic tissue thickness, measured by transmission scanning, and regional ‘thickness’ of blood measured by transmission/emission scanning with direct gravimetric measurements made post mortem. Scanning and direct measurements correlated significantly. 4. In man we used a [99mTc]pertechnetate (99mTcO4) flood source to obtain antero–posterior transmission scans with a gamma-camera. The thickness of attenuating tissue was estimated in each pixel. Scans were obtained of thoracic blood (by labelling erythrocytes with 99mTcO4) and of interstitium (with 99mTc-labelled diethylene-triaminepenta-acetic acid and subtraction of the blood image). We used a computer program to correct the emission scans for attenuation using the transmission scan derived tissue thickness, pixel by pixel. Finally we took a lateral chest radiograph to estimate chest wall thickness. 5. In normal man lung tissue thickness at hilar level was 3.1 ± 0.5 cm (n = 8). Thoracic blood thickness increased from the apex downwards in the upright lung, being 1.2 ± 0.1 cm at the hilar level and 2.0 ± 0.3 cm at the lung base. Interstitial thickness was 0.8 ± 0.3 cm at the hilum and 0.85 ± 0.2 at the base. These values compare well with data in the literature. 6. In emphysema (n = 5) lung tissue and blood thickness were decreased; interstitial thickness was normal. In patients with interstitial pneumonitis (n = 7) lung tissue thickness was approximately doubled, and interstitial thickness similarly increased. In two patients with acute pulmonary sarcoidosis interstitial thickness was not increased despite a marked increase in lung tissue thickness. 7. In conclusion, this technique gives information not readily obtainable by other methods, which may be of clinical utility. Further evaluation and development is warranted.

Mouse glandular kallikreins are encoded by a family of closely linked genes which are located on chromosome 7 at a site corresponding to the genetically defined Tam-1, Prt-4, and Prt-5 loci. We have characterized 24 kallikrein genes by genomic cloning and restriction mapping of 310 kilobase pairs of BALB/c mouse DNA. Most of these genes are highly homologous, have the same exon/intron organization, and are linked in clusters of up to 11 genes. Partial sequence analysis of the kallikrein genes has facilitated identification of those members of the family for which protein sequence data exist and assignment of those which are pseudogenes or encode proteins of unknown function. We find that a maximum of 14 mouse kallikrein genes have the potential to encode functional proteins.

We have used a DNA-cellulose competition assay to investigate the binding of thyroid hormone receptors to fragments of the mouse glandular kallikrein genes and the human and rat GH genes. Nuclear extracts from human lymphoblastoid IM-9 cells were incubated with [125I]tri-iodothyronine ([125I]T3) and DNA-cellulose. The ability of cloned gene fragments to compete for radiolabelled receptors bound to DNA-cellulose was compared with that of DNA from pBR322. As previously observed, a 900 bp fragment from the human GH gene showed preferential binding to the thyroid hormone receptor. High-affinity binding was observed with a synthetic fragment of the rat GH gene encompassing positions − 163 to − 192 but not with a similar fragment from positions −224 to −192. Preferential binding was also observed with fragments of the mouse glandular kallikrein gene, mGK-6. Binding to the entire gene and fragments containing 2300 and 776 bp of the promoter region was identical. Detectable but reduced binding was seen with a shorter fragment. These results suggest that the T3receptor binds to multiple sites within the first 776 bp of the mGK-6 gene promoter. Potential thyroid hormone response elements can be identified within this region of the gene. In contrast, the kallikrein gene mGK-3, which shows a different response to thyroid hormone from that of mGK-6, showed no significant binding in the comparable promoter region.