ClC-3, a member of the large superfamily of ClC voltage-dependent Cl -channels, has been proposed as a molecular candidate responsible for volume-sensitive osmolyte and anion channels (VSOACs) in some cells, including heart and vascular smooth muscle. However, the reported presence of native VSOACs in at least two cell types from transgenic ClC-3 disrupted (Clcn3 −/− ) mice casts considerable doubt on this proposed role for ClC-3. We compared several properties of native VSOACs and examined mRNA transcripts and membrane protein expression profiles in cardiac and pulmonary arterial smooth muscle cells from Clcn3 mice, quantitative analysis of ClC mRNA expression levels revealed significant increases in transcripts for ClC-1, ClC-2, and ClC-3, and protein expression profiles obtained using two-dimensional polyacrylamide gel electrophoresis revealed complex changes in at least 35 different unidentified membrane proteins in cells from Clcn3 −/− mice. These findings emphasize that caution needs to be exercised in simple attempts to interpret the phenotypic consequences of conventional global Clcn3 gene inactivation.

Mosquitonatriuretic peptide (MNP), an uncharacterised peptide from the yellow fever mosquito, Aedes aegypti, acts via cyclic AMP to stimulate secretion of Na Anoga-DH 44 and Anoga-DH 31 were also tested for effects on fluid secretion and ion transport by Ae. aegypti tubules. As in An. gambiae, the CRF-related peptide Anoga-DH 44 had a non-specific effect on the transport of Na + and K + , whereas the CT-like peptide Anoga-DH 31 specifically stimulated transepithelial Na + transport. We conclude that the CT-like peptide Anoga-DH 31 is the previously uncharacterised mosquito natriuretic peptide.

Insect diuretic hormones are crucial for control of water balance. We isolated from the cockroach Diploptera punctata two diuretic hormones (DH), Dippu-DH31 and Dippu-DH46, which increase cAMP production and fluid secretion in Malpighian tubules of several insect species. Dippu-DH 31 and -DH46 contain 31 and 46 amino acids, respectively. Dippu-DH46 belongs to the corticotropin-releasing factor (CRF)-like insect DH family, whereas Dippu-DH 31 has little sequence similarity to the CRF-like DH, but is similar to the calcitonin family. Dippu-DH46 and -DH31 have synergistic effects in D. punctata but have only additive effects in Locusta migratoria. Dippu-DH31 represents a distinct type of insect DH with actions that differ from those of previously identified insect peptides with diuretic activity.Malpighian tubules ͉ corticotropin-releasing factor ͉ Diploptera punctata ͉ Locusta migratoria ͉ Manduca sexta I n insects, urine production by the Malpighian tubules (Mt) is driven by hormonally controlled active transport processes, rather than by ultrafiltration, as in vertebrates. There are several families of insect diuretic peptides, including myokinins, which increase urine production by elevating intracellular Ca 2ϩ (1, 2), and the ''corticotropin-releasing factor (CRF)-like'' diuretic hormones (DH), which act via cAMP (3). CRF-like DH have been identified from eight species in five insect orders (4-14); they are similar to the sauvagine͞CRF͞urotensin I͞urocortin family of vertebrate peptides.For some years, only Manduca sexta was known to possess two CRF-like DH, Manse-DH (4) and Manse-DPII (9). Manse-DPII is shorter (30 residues) than other known DH and has lower sequence similarity with other DH than does Manse-DH. However, in 1998, we identified a second DH from Tenebrio molitor, termed Tenmo-DH 47 (12) to distinguish this peptide from the known Tenmo-DH 37 (11). More recently we identified two DH from Hyles lineata (a sphingid moth closely related to M. sexta), Hylli-DH 30 and Hylli-DH 41 , which each differ at only one residue from their M. sexta counterparts. Thus, in at least three insect species, two DH exist. The extent of sequence similarity between these ''long'' and ''short'' DH indicates that they belong to the same peptide family. However, they are most likely paralogous sequences (arising from a gene duplication event), as is the case for fish CRF and urotensin I. The lower potency of Tenmo-DH 47 vs. Tenmo-DH 37 (12) suggests for it a somewhat different role, just as urocortin, an orthologue of urotensin I (15), has effects that differ in vivo from those of CRF (16,17).We now report the identification of two DH from brain and corpora cardiaca (CC) of the Pacific beetle cockroach (Diploptera punctata), one of which (Dippu-DH 31 ) is a peptide with biological properties that differ from those of the CRF-like DH. Materials and MethodsInsects. D. punctata were maintained as described previously (18). Brains and CC were dissected from adult males 2-10 days old. For bioassays, newly emerged adult males wer...