The physical movement of urine from the kidneys to the urinary bladder and bladder compliance in two anurans.
Urine movement from the ureters to the bladder was accomplished by a combination of gravity and pressures resulting from lung inflation, buccal pumping, and smooth-muscle contraction. Urine movement from the cloaca to the urinary bladder was the result of pressure generated by cloacal smooth-muscle contraction and opposed by urinary bladder pressure, resulting from compliance, lung inflation, and buccal movements. The frequency of cloacal smooth-muscle contraction measured in Chaunus marinus (4.9 min(-1)) and Lithobates grylio (2.8 min(-1)) generated cloacal pressures that averaged 0.67 and 0.59 kPa, respectively. Chaunus marinus had a mean internal bladder pressure of 0.29 kPa, while Lithobates catesbeiana had a mean internal bladder pressure of 0.16 kPa. Using direct urinary bladder infusion and physiological pressure transducers on live anurans, it was determined that urinary bladder compliance was lower (P < 0.05) in the aquatic frog L. grylio (2,050 mL kPa(-1) kg(-1)) than in the terrestrial toad C. marinus (4,440 mL kPa(-1) kg(-1)). Taken together, these data suggest that bladder filling is a result of pressures generated in the ureters and the cloaca that are greater than internal bladder pressures and that the more aquatic species had a less compliant urinary bladder compared with that of the terrestrial species.
Martin
Jon A
JA
Department of Biology, Portland State University, Portland, Oregon 97207, USA. jmart118@uas.alaska.edu
Hillman
Stan S
SS
D000818:Animals; D001001:Anura / Q000502:physiology*; D003187:Compliance / Q000502:physiology; D007668:Kidney / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology; D011312:Pressure; D013045:Species Specificity; D001743:Urinary Bladder / Q000502:physiology*; D014563:Urodynamics / Q000502:physiology*