Novel role of insulin in the regulation of glucose excretion by mourning doves (Zenaida macroura).

In mammals, insulin primarily lowers plasma glucose (PGlu) by increasing its uptake into tissues. Studies have also shown that insulin lowers PGlu in mammals by modulating glomerular filtration rate (GFR). Birds have naturally high PGlu and, although insulin administration significantly decreases glucose concentrations, birds are resistant to insulin-mediated glucose uptake into tissues. Since prior work has not examined the effects of insulin on GFR in birds, the purpose of the present study was to assess whether insulin can augment renal glucose excretion and thereby lower PGlu. Therefore, the hypothesis of the present study was that insulin lowers PGlu in birds by augmenting GFR, as estimated by inulin clearance (CIn). Adult mourning doves (Zenaida macroura) were used as experimental animals. Doves were anesthetized and the brachial vein was cannulated for administration of [14C]-inulin and insulin and the brachial artery was cannulated for blood collections. Ureteral urine was collected via a catheter inserted into the cloaca. Ten minutes following administration of exogenous insulin (400µg/kg body mass, i.v.) plasma glucose was significantly decreased (p=0.0003). Twenty minutes following insulin administration, increases in GFR (p=0.016) were observed along with decreases in urine glucose concentrations (p=0.008), glucose excretion (p=0.028), and the fractional excretion of glucose (p=0.003). Urine flow rate (p=0.051) also tended to increase after administration of insulin. These data demonstrate a significant role for insulin in modulating GFR in mourning doves, which may in part explain the lower PGlu measured following insulin administration.

Lead concentrations of white-winged doves, Zenaida asiatica L., collected in the Lower Rio Grande Valley of Texas, USA.

White-winged dove (Zenaida asiatica L.) exposure to environmentally accessible lead is a management concern. Detectable concentrations of lead were found in 142 (66%) of 214 white-winged doves collected in 2002 and 2003 at two wildlife management units in South Texas. Mean +/- SD lead concentration was 0.70 +/- 1.10 microg/g dry weight and ranged from ND to 11.01 microg/g dw. Lead concentrations were significantly lower in the 2002 samples, but similar between management units, age, and gender. White-winged doves in South Texas are being exposed to lead in the environment with some reaching subclinical to toxic levels.

The relationship between perfluorinated chemical levels in the feathers and livers of birds from different trophic levels.

Although feathers have been used successfully for monitoring heavy metals and organic pollutants, there are currently no data available on the use of feathers as indicators of perfluorinated chemical (PFC) exposure in birds. Also, no study has evaluated PFC levels in birds with different diets from different habitats. In the current study we investigated the PFC exposure of five different bird species from the same geographic region in Belgium, using both feathers and liver tissue. The highest mean liver perfluorooctane sulfonate (PFOS) levels were found in the Grey Heron (476 ng/g ww) followed by the Herring Gull (292 ng/g ww) and Eurasian Sparrowhawk (236 ng/g ww), whereas the Eurasian Magpie (17 ng/g ww) and the Eurasian Collared Dove (12 ng/g ww) had the lowest levels. The PFOS levels in the feathers showed a different pattern. The Grey Heron had the highest feather PFOS levels (247 ng/g dw), the Eurasian Sparrowhawk (102 ng/g dw) had the second highest feather PFOS levels, followed by the Herring Gull (79 ng/g dw) and the Eurasian Collared Dove (48 ng/g dw), and the lowest levels were found in the Eurasian Magpie (31 ng/g dw). Overall, there was a significant positive correlation (Pearson, R=0.622, p<0.01) between the feather and liver PFOS levels, indicating that feathers could be an alternative bioindicator for PFOS exposure in birds. However, caution should be taken as there was no significant correlation between the PFOS levels in the feathers and livers of the individual species. In general, birds from a higher trophic level had higher PFC levels in their tissues. This indicates that diet plays a role in PFC exposure in birds and confirms the bioaccumulation potential of PFC.