BUENOS AIRES, April 28 (Reuters) - Argentina's stock, currency and bond market trends on Tuesday:
* The MerVal stocks index .MERV extended its losses for a second straight session, tracking Wall Street, which fell on worries that major banks may need more capital.
* Tenaris TENA.BATS.N, which makes steel pipes for the energy industry and is weighted as almost half of the MerVal, retreated 0.43 percent to 46.8 pesos per share.
* On the broader market, volume was a slack $4.5 million, with more than half in Tenaris.
* Prices for government bonds traded over the counter in Buenos Aires also fell, sliding 1.7 percent on average in light trade as investors pocked profits from recent gains..
* Peso-denominated Disc bonds ARDISCP=RASL shed 4.9 percent, according to the ask price.
* In formal exchange between banks, the peso fell 0.34 percent to 3.715/3.7175 per dollar ARS=RASL.
* In informal trade between foreign exchange houses as measured by Reuters, the peso retreated 0.13 percent to end at 3.74/3.745 ARSB=. (Reporting by Walter Bianchi and Jorge Otaola; Writing by Kevin Gray; Editing by Dan Grebler)