Antidiuretic hormone (ADH) is produced by the hypothalamus and released by the pituitary gland to control water balance in the human body.
ADH regulates the permeability of the kidney tubules to control how much water is reabsorbed.
Table 1 displays clinical data showing the effects of different blood plasma concentrations of ADH on urine flow rate and urine concentration (measured as osmolality).
Table 1
| Blood ADH concentration in pmol/dm3\text{pmol/dm}^3pmol/dm3 | Osmolality of urine in mOsm/kg\text{mOsm/kg}mOsm/kg | Rate of urine flow in cm3/minute\text{cm}^3/\text{minute}cm3/minute |
|---|---|---|
| 1.5 | 250 | 10.5 |
| 3.0 | 500 | 7.2 |
| 6.0 | 950 | 3.5 |
| 9.0 | 1120 | 1.8 |
| 12.0 | 1250 | 0.8 |
During a prolonged training session without water intake, an athlete's blood ADH concentration increases from 3.0 pmol/dm33.0\text{ pmol/dm}^33.0 pmol/dm3 to 9.0 pmol/dm39.0\text{ pmol/dm}^39.0 pmol/dm3.
Explain how this increase in blood ADH concentration causes the changes to the urine shown in Table 1.