title: The effect of prenatal exposure to carbon monoxide on breathing and growth of the newborn guinea pig.
abstract: In utero hypoxia may affect the development of the brain and result in altered respiratory responses postnatally. Using a barometric plethysmograph, we examined the effects of exposing pregnant guinea pigs to 200 ppm carbon monoxide (CO) for 10 h/d from d 23-25 of gestation until term (approximately 68 d) on the ventilatory responses of their 4-5-d-old neonates at rest, and during progressive asphyxia and steady state hypercapnia. Exposure to this concentration of CO produced significantly higher levels of carboxyhemoglobin (COHb) in maternal (8.53 +/- 0.6% versus 0.25 +/- 0.1%) and fetal blood (13.0 +/- 0.4% versus 1.6 +/- 0.1%) from CO-treated animals when compared with controls. Hematocrit was significantly higher in the CO-treated neonates (46.3 +/- 1.0% versus 41.3 +/- 0.9%) at 5-6 d of age, although no difference existed between the groups for COHb at this time. There was no difference between the groups for length of gestation, litter size, or birth weight, but CO-treated neonates were significantly smaller at 4 d of age (102.4 +/- 3.7 g) compared with controls (132.0 +/- 5.0 g). At 4-5 d of age there was no difference between the groups for either tidal volume (VT), respiratory frequency (f), or minute ventilation (VE) at rest, but during steady state hypercapnia (4 and 6% CO2) the CO-treated neonates had a significantly greater VT and VE (but not f) than did controls. During progressive asphyxia, CO-treated animals had a significantly greater VT than did controls from 1-8% CO2. There was a significant fall in f at 1 and 3% CO2 in CO-treated animals; however, this effect did not persist, resulting in a significantly increased VE from 3 to 8% CO2. The inspiratory flow rate (VT/expiratory time) was significantly increased in the CO-treated neonates during progressive asphyxia; this occurred in the absence of a difference in inspiratory time between the groups. These results indicate that prenatal exposure to CO increases CO2 sensitivity in 4-5-d-old guinea pigs. This may be due to developmental alterations in the areas of the brainstem responsible for respiratory control.
authors.affiliation: Department of Physiology, Monash University, Clayton Victoria, Australia.
authors.forename: H P
authors.initials: HP
authors.lastname: McGregor
authors.forename: K
authors.initials: K
authors.lastname: Westcott
authors.forename: D W
authors.initials: DW
authors.lastname: Walker
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002248:Carbon Monoxide / Q000633:toxicity*; D005260:Female; D006128:Growth / Q000187:drug effects*; D006130:Growth Disorders / Q000151:congenital*; D006168:Guinea Pigs; D018811:Maternal Exposure; D011247:Pregnancy; D012119:Respiration / Q000187:drug effects / Q000502:physiology*
chemical_list: D002248:Carbon Monoxide